Impact of oils and coatings on adhesion of structural adhesives

Marcus HagströmThesis project for the degree Master of Science

Royal Institute of TechnologySweden

September 24, 2015

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Acknowledgements

I want to thank my supervisors Lina Orbèus(Scania), Jessica Andersson(Swerea Kimab), Malin Torn-beg(Swerea Kimab) and Magnus Burman(KTH) for helping me with tasks such as technical support,feedback and discussions. I also want to thank Tania Irebo and Arne Bengtson for help with UVF,Dan Persson for help with FTIR scanning and Eva Hagström for help with introduction and set up foradhesive testing.

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Abstract

This is a master thesis project conducted for Scania CV AB in collaboration with Swerea Kimab. Thepurpose is to examine how oils and coatings on the surface affect the adhesion of adhesives. Earlier workdone by Scania indicate that the amount of oil applied may have an impact on the adhesion. Substratestested are hot dipped galvanised steel, electro galvanised. AlSi and ZnMg. Oils used are Anticorit RP3802 that is an anti-corrosive oil and Renoform 3802 that is a drawing oil. The two adhesives used areBetamate 1496f and SikaPower 498.

The performance of adhesive bonds is strongly dependent on the surface it adheres to and any contam-inates such as oil present on the surface. These factors may greatly decrease the performance of thebond. There are adhesives that have been designed to tolerate a specific amount of oil on the surfacesand should develop a satisfactory bond with oil present.

This project has firstly developed a routine for easy application of oil with the result of a known amountof oil and a uniform oil distribution on the surface of the coated sample. Secondly lap-shear tests havebeen performed for various amounts and types of oil in combination with four different coatings and twoadhesives. For the evaluation of failure mode a program using k-mean factoring was written to providean objective method to characterise the bond.

Lap-shear tests show that there does not seem to be any apparent difference in bond strength for variousamounts of oil and for the two different adhesives except for one combination. Even thought the twoadhesives develop the same strength the failure mode differs between the two.

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Contents

1 Introduction 1

2 Literature Study 22.1 Adhesion Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.1.1 Specific adhesion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.1.2 Mechanical Adhesion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.1.3 Thermodynamic Work of Adhesion . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Surface Characteristics Affecting Adhesion . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2.1 Surface Energy and its Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . 42.2.2 Wetting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.2.3 Surface Roughness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.3 Adhesive Bonds and Test Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.3.1 Adhesive Failure Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.3.2 Peel Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.3.3 Lap-shear Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.4 Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.4.1 Galvanized Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.4.2 ZnMg Coated Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.4.3 AlSi Coated Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.5 Oil Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.5.1 Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.6 Surface Roughness Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3 Material 103.1 Oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.1.1 Adhesives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.1.2 Sheet Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4 Experimental 114.1 Oil Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4.1.1 Sample Size and Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.1.2 Surface Treatment Prior to Oil Application . . . . . . . . . . . . . . . . . . . . . . 114.1.3 Cleaning of Sheet Metal Specimens . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.1.4 Oil Application and Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.1.5 Oil Analysis of oil distribution and amount of oil . . . . . . . . . . . . . . . . . . . 12

Weighing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12UVF-Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12NIR-spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.2 Adhesion Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.3 Sample Size and Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.4 Surface Treatment prior to bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.5 Adhesive Application and Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.5.1 Bonding Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.5.2 Adhesive Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.5.3 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.6 Surface Profile Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

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5 Result 175.1 Oil Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5.1.1 Amount of oil applied . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195.2 UVF Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195.3 NIR Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.4 Tensile Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

5.4.1 Roughness Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225.4.2 FTIR Scans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

6 Discussion 246.1 Oil Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246.2 Lap Shear Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

6.2.1 HDG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266.2.2 Electro galvanised . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266.2.3 ZnMg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266.2.4 AlSi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

6.3 Material Impact on joint strength discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 276.4 Adhesive Properties and handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276.5 Bond geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

7 Conclusion 29

Appendix A UVF Results 31

Appendix B Tensile Tests 36

Appendix C Adhesive Bond-SikaPower 498 44

Appendix D Adhesive Bond-Betamate 1496 48

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Chapter 1

Introduction

Adhesive bonding as a joining technique has grown in popularity and implementations with the intro-duction of ”new” material concepts such as composites and sandwich structures. The bonding of thesematerials and between dissimilar materials(multi-material bonding) such as thermoplastics to aluminiumor steel can not usually be done using traditional welding techniques and therefore requires alternatejoining methods such as adhesive bonding. Additional benefits of adhesives is its non-existence of a heataffected zone or a very low heat input not resulting in any build up of stresses or distortions. The use ofadhesive may also results in a lower overall weight. In addition from using adhesives for bonding thereare mechanical methods of fastening that can be used. The drawback of these methods is its inherentdeformation of the material/geometry and that the joint may give rise to stress concentrations at thehole edges. For Scania adhesives are used in combination with spotwelding in so called weldbonds. Theupside of this bond type is the spotwelds mechanical performance with the adhesive bond extending thefatigue life of the joint.

For all its benefits, adhesives still have a few challenges. The bonds made are usually not as strongwhen compared to welds and are more sensitive to the direction of the applied force. They also havea dependency on the surface condition of the material. A contaminated surface can result in greatlyweakened bonds hence surface preparation is important.

This report is the result of a master thesis project done at Swerea Kimab and Scania. The purposeis to examine how oils and coatings on the surface affect the adhesion of adhesives. Earlier work doneby Scania indicate that the amount of oil applied may have an impact on the adhesion. The project issplit into three different parts: evaluation of controlled method for applying oil, verification of amountof oil applied, and testing of adhesion properties. The test involves two adhesives Betamate 1496 andSikaPower 498, through the report these are either mentioned by their full name or as Betamate andSika.

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Chapter 2

Literature Study

2.1 Adhesion Theory

According to European standard the definition of adhesion is “State in which two surfaces are heldtogether by interfacial bonds” [1]. This standard definition of adhesives explains what adhesion is (inter-facial bonds) and it defines its nature but not how to quantitatively measure it or how its characteristicsare specified. This is most likely due to the numerous variables involved in the testing. Stating that theadhesion of material X to material Y is Z implies the same characteristics and variables for all the timesX adheres to Y, everything is kept constant. Changing thickness of the adhesives coating or slightlychanging the surface preparation can lead to widely different results resulting in material X to materialY is not Z. Thus some universally measurable characteristic of adhesion is hard to apply. Lacombediscusses this in Adhesion Measurement Methods, Theory and Practice [2] and in his discussion states:

Qualitatively we might say A has good adhesion to B based on the observation that A wasnever observed to separate from B under a variety of common loading conditions.

From this it can be derived that ”good adhesion” is only observed for those loading conditions that whereactive. Changing some loading condition changes the adhesion characteristics and earlier observation ofgood adhesion are not valid for the new conditions.

Different theories have been developed as to how the two surfaces are held together, what is causing theinterfacial bond. The theories can be split into two categories mechanical and specific adhesion. Specificadhesion being the molecular attraction between surfaces. Mechanical adhesion is when the structure ofthe surfaces(surface profile) pressed together result in adhesion.

2.1.1 Specific adhesion

Specific adhesion is split up into theories such as polarisation, diffusion, chemical, electro statical andthermodynamic adsorption. For optimal bond strength probably as many of the below mentioned adhe-sion mechanics should be active.

Polarisation theory for adhesion was developed in 1935 and explains adhesion with the polar nature ofcertain molecules. The polar nature gives rise to attractive forces between surfaces and thus makingthem adhere. Molecules do not carry any overall charge but for molecules that includes two atoms ofdifferent atomic numbers the larger atom will cause a shift of the electrons towards itself creating anelectronegative area giving rise to a dipole. One simple example of this is H2O. Water is a permanentdipole because of its geometry and atoms. The oxygen atom attracts electrons from the hydrogen creatingan electronegative area whilst the hydrogen atoms gets a positive area, creating a permanent dipole.

Apart from permanent dipoles the intermolecular interaction can also be generated by induced dipolesor dispersion forces. Induced dipoles are the result of permanent dipoles inducing polarity on closeproximity molecules that do not have any polarity. Dispersion or The London-van der Waals force isdescribed according to Myers,1991[3] as a quantum mechanical force in nature as it involves rapidlyfluctuating dipoles resulting from the movement of the outer-valence-shell electrons.

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Diffusion is as the name implies a phenomenon that can occur during bonding of polymers as they arenot fully static systems. The molecules move ever so slightly and when two surfaces come into contactthe surfaces will entangle into each other. This entanglement creates a bond holding the two surfacestogether. For metals as opposed to polymers diffusion is not likely. If the adhesive and surface to bebonded contains reactive molecules the two components can react with each other and form chemicalbonds at the interface thus joining the surfaces. The electro statical theory explains adhesion with thetransferral of electrons between two surfaces. This transference between layers forms an electrical doublelayer which gives rise to an attractive force [4].

Thermodynamic Adsorption

The adsorption theory after Zisman, Fowkes, Good and Wu is one of the newer(1963) theories used todescribe adhesion. It states that if two surfaces come into close enough contact they will bond due tointer-molecular and atomic forces. Close enough contact is that the surfaces need to be in at least 5Å (5 · 10−7mm) for the forces to be active as shown in Figure 2.1 below.

Figure 2.1: Bonding energy as a function of distance, Åke Dolke Kompendium KTH(2012)

2.1.2 Mechanical Adhesion

Mechanical adhesion is explains adhesion with that rough profiles on two surfaces pressed together createsfriction and through friction achieves adhesion but as the surface profile roughness is only seen throughmicroscopy analysis this is most likely negligible. The roughness of the surface instead creates a largerarea for the adhesive to come into contact with the substrate resulting in stronger adhesive bonds. Therough surface enables the adhesive to better interlock with the surface by filling in all the microscopicmountainous terrain.

2.1.3 Thermodynamic Work of Adhesion

The thermodynamic work of adhesion can be mathematically formulated and is described as the energyto separate two faces. The work is described by Duprés equation and can be used to better understandand calculate on the adhesion of bonds.

Wadh = γS + γLV − γSL (2.1)

where γS is the surface free energy of the solid, γLV is the surface free energy of the liquid and γSL isthe interface energy between solid and liquid. So knowing the energy between the components one cancalculate the work of adhesion. One should keep in mind that the above equation only takes into accountthe van der Waals forces [5] or the primary bonds(ionic and covalent). It also excludes the mechanicalinterlocking. It does not by itself either give any information on the failure kinetics of the bond.

2.2 Surface Characteristics Affecting Adhesion

There are two surface characteristics that give a good indication on how the adhesion of the adhesive toan adherent will be. Here is the surface energy and the topology of the surface, its roughness. The surfaceenergy influences the wetting(spread and adherence) characteristics and is essential to achieving a good

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coating with the adhesive. A surface with high roughness has a greater area exposed to the adhesive tobond with and become ”interlocked” with the surface compared to a very fine(little roughness) surface.

2.2.1 Surface Energy and its Measurement

Surface energy arises due to the fact that atoms or molecules at the surface of a bulk differ in their netforce compared to those in the bulk. Studying a molecule or atom surrounded by other molecules oratoms the total force acting on the unit will be zero. A unit at the surface will not have a total force ofzero due to the non-homogeneous distribution of units around that one unit. This gives rise to a totalforce acting inwards towards the bulk. As described by Myers,1999 [3] one can look at this phenomenonas a spring model. The interfacial molecules are pulled into the bulk resulting in a net density decreasingfor the surface and the springs between the molecules growing tighter as the molecule is pulled inwards.The force from the tightening of the springs is what is called the surface energy or tension. The aboveworks well when describing the surface tension of liquids but when looking at solids the spring methodcan become quite complicated as the forces are not necessarily acting in all the same direction (solidsurfaces are usually rough and jagged). Therefore when dealing with solid surfaces the term surfaceenergy instead of tension is used. Metallic surfaces tend to have a high surface energy leading to an easywetting of the surface.

2.2.2 Wetting

In order to achieve a high thermodynamic work and thus good adhesion wetting of the surface is needed.Wetting is also an important characteristic as it results in a good(or bad) spreading of the adhesion onthe surface and thus impacting on the adhesive quality of the bond. Wetting of a surface is dependenton the surface energy of the solid and the liquid. The relationship between these two defines if goodwetting will be achieved. Therefore knowing your surface and liquid can in an early stage of productdevelopment or testing give an idea of how the two will work together and if any surface pretreatmentis needed. Figure 2.2 from Dolk [6] gives a principle picture of a drop of liquid on a surface and thedifferent surface energies involved.

Figure 2.2: Liquid solid contact angle on surface, Dolk [6]

For full wetting of the surface the angle (θ)angle between γSL(surface tension solid/liquid interface)and γLV (surface tension liquid)) is to be close to zero, the liquid will then flow along the surface. γSrepresents the surface energy of the solid. From Figure 2.2 above the relationship between the surfacetensions can be described by Youngs Equation below.

γS − γSL = γLV · cos(θ) (2.2)

As mentioned in order to achieve full wetting the angle needs to be close to zero, θ → 0. This criteriainserted in Equation 2.2 results in the below relationship.

γS ≥ γSL + γLV (2.3)

From Equation 2.3 it is seen that to achieve wetting of the surface the free surface energy of the solidneeds to be greater than the sum of the liquid and interfacial energy. Hence having a high surface energymaterial will make wetting of the surface easier. In general metals exhibit a relatively high surface energyas compared to plastics.

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2.2.3 Surface Roughness

Visually without any help from instruments the surface of most objects seem to be smooth and displaya low roughness. With the help of for example an electron microscope the surface will probably moreresemble a mountainous and very rough terrain. The closer you look the rougher the surface appears.For most applications a smooth surface is desirable but for adhesives a rough surface can promote ahigher degree of bonding due to an added surface area as shown in Figure 2.3.

Figure 2.3: Adhesive fully penetrating rough surface

To achieve this the adhesive needs to have a low viscosity to be able to penetrate the surface and attainfull contact with the substrate. If this is not the case the adhesive might only bond to the upper top ofthe surface profile as shown in Figure 2.4, resulting in weaker bonds.

Figure 2.4: Adhesive adhering to top of surface

How well the adhesive adheres to the surface is thus dependent on the characteristics of the adhesive.A low viscosity adhesive will easier coat the whole surface compared to a high viscosity adhesive. Inorder to achieve good wetting the adhesive should have a low viscosity and be given sufficient time towet the whole surface. Therefore a fast curing adhesive with high viscosity will not have time to fullywet the entire surface and may look more like Figure 2.4 instead of the more ideal case in Figure 2.3. Anexample of this is given by Dolk [6], two different epoxy adhesives with viscosity of 10000mPa · s and200000mPa · s both at 25° are allowed to wet a surface. The time until maximum possible wetting wasachieved was measured. For the lower viscosity adhesive the time was 15minutes and for the higher itwas 200minutes. From this it can be concluded that the viscosity of the adhesive has a large impact onthe wetting of the surface and that the time allowed for the adhesive to fully coat the surface matters.

2.3 Adhesive Bonds and Test Methods

There are numerous ways to design an adhesive bond and the strength of the bond greatly depends onhow the stress travels throught the joint. The evaluation of the characteristics of an adhesive bond ismostly done with mechanical testing and results in some kind of bond strength value. In principle thereare five ways to stress an adhesive bond, in shear, pull, peel, pressure and cleave. These are shownin Figures 2.5. In general the optimal stress for an adhesive is shear and worst is usually in peel butthis also very much depends on the type of adhesive used. This is easily exemplified with post-it cards.Creating a lap-shear bond with two post-its and pulling they will withstand some force. Subjecting thepost-it bond to a peel force much less force is needed to separate the surface.

(a) Pull (b) Pressure (c) Shear (d) Peel (e) Cleave

Figure 2.5: Adhesive Bonds

For the pressure and tensile design the forces will be distributed over the whole adhesive area. In peel orcleave only a part of the bond will be subjected to the forces resulting in high local stresses. For shearthe force will be distributed over the whole area.

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2.3.1 Adhesive Failure Modes

There are essentially two failure modes when dealing with adhesives testing; adhesive and cohesive failure.Adhesive failure denotes separation that appears visually to be in the interface between two phases, 2.6a.Cohesive failure implies only visible separation in one of the phases, 2.6b. This can either occur in theadhesive or the material bonding with the adhesive. According to Lee [5] adhesive failure may not occurbut be a cohesive failure very close to the surface not detected by the naked eye.

(a) Adhesion Failure (b) Cohesion Failure

Figure 2.6: 100% adhesive or cohesive failure

Performing destructive testing either the adhesive or the substrate can fail. The substrate can fail eitherby delamination, cohesive or fracture. The adhesive can fail as described above by adhesive or cohesivefailure but might not always be such straightforward modes as one of the modes. Failure can also be acombination of both modes as displayed in Figure 2.7 below. Delamination between the coating and thecore metal of the sample may also occur. A full list of the failure modes and definitions can be found inEN ISO 10365 [7].

Figure 2.7: Combined Adhesion Cohesion Failure

2.3.2 Peel Test

Peel testing is a method to test the adhesion of adhesives and is a method that subjects the adhesiveto a non optimal load case for an adhesive bond. The test can be done in various ways, three commontechniques are the 90°, 180° or a T-peel test. The choice of method depends on the adherents that areto be bonded.

(a) 90° − Peel (b)180° − Peel

(c) T-Peel

Figure 2.8: Peel Test Methods-Dolk 2012 [6]

The 90° test method is usually used to test the peel resistance when at least one of the adherents areflexible. To keep the angle at a constant 90° angle during test the rigid fixture needs to be able to rollhorizontally during testing to be able to stay constantly under the pulling rigs grip. The 180° peel testis closely related to the 90° method. The implications of the 180° compared to the 90° is that there arelarger deformations on the adherent being bent and therefore it needs to be more flexible as to not failduring testing. To perform a 180° or 90° you therefore need one rigid and one flexible adherent. Duringthe T-peel test the adherents must have the same characteristics in order to deform equally. If the T-peeltest is performed with adherents of different rigidity the bond will rotate and the crack will propagateand move toward the thinner(less rigid) adherent [8].

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2.3.3 Lap-shear Test

Lap-shear testing of adhesives is a relatively fast and simple way to determine the strength of an adhesive.The bond is pulled as in Figure 2.9 and is subjected to shear loads until it fails.

Figure 2.9: Shear Testing-Dolk 2012 [6]

One drawback of the method is the asymmetrical load on the bond. According to Bonk et al. [9] theshear stress at the edges have been found to be as high as 6 times the average stress due to the rotationof the bond, as seen in Figure 2.10.

Figure 2.10: Rotation of lap-shear bond-Dolk 2012 [6]

Therefore the load at failure divided by bond area does not relate to the maximum stress at failure.In the use of stress analysis the data collected from these tests are limited but as quality control andcomparison of adhesives it will suffice [5].

2.4 Coatings

During this project four different coatings will be evaluated, hot dipped galvanised(HDG), Zinc Magne-sium (ZnMg), electro galvanised(EG) and Aluminium Silicon(AlSi). These coatings are applied to protectsteel from corrosion and the different coatings all exhibit different corrosion resistance characteristics.

2.4.1 Galvanized Steel

A process that is widely used in the industry to protect against corrosion is the galvanisation process,applying a zinc layer to the steel. The zinc coating works as a corrosion resistant surface and as angalvanic anode for the steel. Two methods to coat are Hot-dip galvanization and electroplating. Hot-dipgalvanization involves dipping the steel into a molten zinc bath and in such a way coating the steel.The zinc melt may also be alloyed with other elements to change the surface characteristics [10]. Thesealloys affect the characteristics of the Zinc layer and according to Gaillard et.al. surface enrichment ofAl may reduce the adhesion [11]. Electroplated uses electrolysis to create a thin pure zinc layer on thesteel sheet. Usually the electroplated layer is thinner than the HDG.

2.4.2 ZnMg Coated Steel

Historically zinc coatings have been used as a corrosion protection but under severe conditions the zinccoating has been found not to be satisfactory [12]. New coatings have been developed that have bettercorrosive properties under severe conditions and one of those is ZnMg. Dutta et.al. shows that a coatingof Zn with 2.5%wtMg has a better corrosion resistance compared with pure zinc. It is to be notedthat best corrosion resistance was found to be with Zn − 0.4%wtMg − 0.25%wtAl [13]. Testing doneby Scania [14] shows that while the lap-shear strength requirements specified by Scania are fulfilled thefailure mode is roughly 100% adhesive and this is not optimal and are not within requirements.

2.4.3 AlSi Coated Steel

AlSi coating are done to protect bare metals against corrosion and also offers a good protection againstscaling(build up of hard mineral coatings) [15]. The corrosion protection is acceptable but only worksas a barrier effect [16]. The steel used is often boron steel coated with AlSi. This combination producesa very hard steel with corrosive resistant properties.

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2.5 Oil Analysis

Oil analysis in this report relates to the weight of oil and methods of analysing the surface of the oilfilm.Determining the weight of the oil can easily be done in a non-destructive way by weighing the samplesprior to application and then after, the difference represents the amount of oil applied. The level ofoil film on the surface can be analysed using some form of spectroscopy such as near-infrared(NIR) orultraviolet florescence(UVF) while chemical information can be analysed by fourier transform infraredSpectrometry(FTIR).

2.5.1 Spectroscopy

Spectroscopy encompasses the study of electromagnetic radiation and materials. A part of the electro-magnetic spectrum is the visible radiation we see. The rest is other forms of radiation and using otherdetection devices apart from the human eye it can be visualised. To register this radiation a spectrum oflight can be directed at a material that will react and send out radiation. By measuring this radiationinformation about the material can be found.

UVF registers the florescence light sent out by certain molecules. In this project the application area isto determine the oilfilm distribution. UVF is suited for this as most oils contain hydrocarbons and whenhydrocarbons are illuminated with a certain light they are excited and send out florescent light. Theintensity of the light is proportional to the oilfilm thickness [17]. With this a mapping of the topographyfor the oil film can be seen as a function of intensity but any absolute data on the film thickness orrelative changes on the film cannot be taken. An examples of this is shown in Figure 2.11 that shows aclean sample with three drops of oil applied.

Figure 2.11: Initial test of UVF

The three drops are clearly seen with a clear distinction between sample and oil. The top(thickest) partsof the oil drop show a higher intensity. NIR works in principal the same way as UVF but with thedifference that the radiation analysed is in the near-infrared region. FTIR is used to identify substancesin samples. The sample is scanned and results in a spectrum displaying the absorption of differentwavelengths. These wavelength correspond to bonds and thus the bonds(and therefore the components)in a sample can be determined.

2.6 Surface Roughness Analysis

Surface roughness can be analysed using either optical or contact measurements techniques, in this projectcontact measurement is used. A stylus is placed on the surface and then moved over the samples. Thechanges in surface profile are registered. Figure 2.12 shows the surface profile of HDG and electroplatedsteel.

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Figure 2.12: Example of Surface Profile

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Chapter 3

Material

3.1 Oils

Two types of oils will be used in this project while testing of the adhesives.

Designation Supplier Density [kg/m3] Viscosity [mm2/s]Anticorit RP 3802 S (190kg) Fuchs 894 (15 ) 33.5 (40 )

Renoform MCO 3802-SN Fuchs 918 (15 ) 100 (40 )

3.1.1 Adhesives

Two adhesives will be used during the adhesive testing. Both are epoxy adhesives that are designed towithstand oil. The adhesives are Betamate 1496F and SikaPower 498.

Designation Lap Shear Strength[EN1465] [MPa]

E-Module[MPa]

Curing Type Max oil g/m2

Betamate 1496f 31 1400 Heat Epoxy 5SikaPower 498 20 - Heat Epoxy Hybrid 2

3.1.2 Sheet Material

Four materials will be evaluated. They all have a different thickness and will therefore have differentmechanical properties.

Coating Quality Thickness [mm] DesignationZ100 (HDG, 100g/m² (7,5µm/side)) DX56D 1.5 Z100

ZE75/75 (electroplated with 7,5µm/side) DC06 0.75 ZE75/75ZM100 (ZnMg, 100g/m²) DX54D 0.8 ZM100Boron steel with AlSi150 22MnB5 1.1 AS150

10

Chapter 4

Experimental

4.1 Oil Application

Various oil application methods are tested and evaluated based on aspects such as ease of use andamount of oil. The sample metal used is a hot-dipped galvanized steel from Scania’s production unit inOscarhamn. 1

4.1.1 Sample Size and Preparation

The sheet sizes are delivered as A4 and are needed to be cut. The samples are cut to a length of 130mmand width of 25mm. The samples are either stamped with an identification number or marked with apermanent pen after cleaning.

4.1.2 Surface Treatment Prior to Oil Application

The samples are coated with oils from the factory and other contaminates deriving from transport orcutting of samples. In order to achieve a known surface for further oil application the surface is cleaned.This is done mechanically and chemically, the process is described below. The samples are handled usingtweezers and magnets in order to avoid contamination of the surface.

4.1.3 Cleaning of Sheet Metal Specimens

1. Using kitchen roll paper and acetone the samples are wiped to remove dirt and excess oil.

2. The samples are then placed in an ultrasonic bath of acetone for 5min.

3. After the bath the samples are rinsed in a washing bottle filled with acetone and then placed in afixture for drying.

4. The samples are checked and if visual stains are present the above steps are repeated.

The samples are stored in plastic bags until weighing.

4.1.4 Oil Application and Measurement

Five different application methods are tested; Mayer-rod coating (barcoating), dipcoating, spraycoating,kitchen cloth (Wettex) and kitchen sponge. Initially an evaluation of the application techniques are done.Spray worked well under calibration/tests with water but not for oils due to the higher viscosity.

For dipcoating one side of the sample is dipped into an oil bath and kept there until the whole side iscoated. The sample is then removed and held upright letting excess oil drip off. The sample is thenplaced on a rack as shown in Figure 4.2a. Barcoating is done using a Mayer-rod and an improvisedapplication table. The Mayer-rods are numbered corresponding to size, larger number deposits a larger

1It is not the same HDG-metal as the one used during the adhesive tests.

11

amount of oil in theory. Oil was applied on the sample using a pipette and then carefully spread outusing a Mayer rod(Nr.1), shown in Figure 4.1 below.

Figure 4.1: Mayer rod application setup

For cloth and sponge oil is applied on the applicator(cloth or sponge) using a pipette, once the clothis soaked it is pulled over the sample until it is fully coated. The samples are stored in a rack, nearhorizontal until further use(not a fixed time) as shown in Figure 4.2a. Other orientations of the samplesduring storage is also evaluated, Figure 4.2b.

(a) Vertical (b) Horizontal

Figure 4.2: Stoage orientations for oiled samples

4.1.5 Oil Analysis of oil distribution and amount of oil

To evaluate and determine a routine for oil application different analysis techniques are used to measurehow the oil is distributed on the sample once coated. Weighing is used for determining the amount ofoil whilst spectroscopy is used for surface evaluation.

Weighing

Weighing is done prior to oil application and then immediately after. The difference in weight correspondsto the applied amount of oil. Mettler Toledo AE240 is used for weighing. It is calibrated with its internalweight(100g) before starting and a plastic holder is used as a fixture for the sample. The samples are leftfor about 60 seconds or longer depending on the time it takes for the result to stabilize. The accuracyis down to 5 decimals (0.1mg) but the last decimal was discarded due to fluctuations. Measurements ofa few samples is done continuously to investigate the impact of runoff over time.

UVF-Spectroscopy

The samples are illuminated using a LED light powered by a direct current power supply. The returningflorescent light is captured and run through a filter(> 360nm). The whole UVF testing is controlledusing a written Labview program. The sample area scanned as shown in Figure 4.3 is 50mm x 20mmwith a step length of 2mm.. The area to scan is chosen to correspond to the area to be bonded.

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Figure 4.3: Scan area for UVF

NIR-spectroscopy

Near infra-red spectroscopy is briefly used on a few samples in order to test a NIR-scanning equipmentand its uses for analysing oiled surfaces. This test is thus only used for testing the equipment and is notactually used on all the samples. Even though the results from the analysis can be used for this project.The whole samples are scanned and the resulting data is manipulated to produce a clear picture of thesurface.

4.2 Adhesion Testing

Adhesion of the adhesives and substrates are evaluated by lap shear tests done according to SS-EN1465:2009[18]. Two oils, two adhesives and four different coatings are evaluated. To account for possiblespread in the result three samples of each combination of oil/coating is done. For reference tests fivesamples are made.

4.3 Sample Size and Preparation

The samples are cut to the dimensions specified in SS-EN 1465:2009, length of 100mm ± 0.25mm andwidth of 25± 0.25mm. The thickness of the test samples differ between 0.8mm− 1.5mm. The coatingsare then stamped with a alphanumeric combination for identification.

4.4 Surface Treatment prior to bonding

The surface treatment and cleaning follows the same procedure as for oil application. The panels arethen weighed before application of oil and panels not to be used immediately are placed in individualairtight bags and then into a larger airtight bag containing a desiccant bag.

Re-application of oil

The oil is applied using a kitchen cloth that has been coated with oil. The cloth is wiped across thesample surface multiple times until the whole surface is covered. The panels are then weighed and theamount of oil is determined. If a too large quantity of oil is applied removal of oil is done by applyinga paper cloth and pressing it to the surface with care taken not to wipe the surface. The cloth is thencarefully pulled off and the sample is weighed again. This process is repeated until the correct amount ofoil is achieved. Reapplication of oil may be necessary if too much oil is removed. To remove any gradientfrom runoff or handling the samples are flat in the fixture for 1 hour enabling the oil to float out anddevelop a more uniform surface.

4.5 Adhesive Application and Curing

Adhesive application is done according to Scania Standard STD 4440 were applicable.

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4.5.1 Bonding Assembly

The oiled panels are placed in a fixture where the dimension of the bond area and samples can accuratelybe controlled. The bond thickness is controlled using teflon tape with a thickness of 0.2mm. The tapeis placed on either side of the adhesive bond to ensure a uniform thickness, Figure 4.4a. The samplesare screwed down by hand to supply pressure and attain the correct thickness, Figure 4.4. A probe formeasuring object temperature is also fixed to one sample.

(a) Teflon Tape (b) Bonds ready forcuring

Figure 4.4: Bonding Assembly

4.5.2 Adhesive Application

The adhesives are supplied in cartridges and thus a cartridge gun is used for application of the adhesive.The cartridge gun heats the adhesives and uses air pressure for controlled application. The adhesivesare placed in the cartridge gun and the temperature is set to 60 for Betamate 1496f and 55 forSikaPower 498. They are left in the cartridge gun for 1hour to ensure the adhesive has achieved thecorrect temperature. After 1hour the pressure is set to 4bar for Betamate 1496f and 2.3bar for SikaPower498. Theoretically the amount of adhesive to be applied has a volume of 25x12.5x0.2mm = 62.5mm3 inpractice an excess of adhesives is applied and allowed to be squeezed out in this way ensuring that thebonding volume is filled, Figure 4.5.

Figure 4.5: Adhesive Application

4.5.3 Curing

The adhesives are cured in a pre-heated oven, temperature set to 190. The object temperature ismeasured with a Fluke CNX t3000 K-type thermocouple with a probe placed on the surface duringcuring. When the object temperature reaches 180 timer set for 8minutes is started. Samples are thenremoved and left to cool at room temperature. Once cooled the samples are stored in individual plasticbags contained in a larger plastic bag with an desiccant bag.

Mechanical Testing

Testing is done according to SS-EN 1465:2009 [18]. Tensile testing is done with an Insitron 5500 runningsoftware series IX version 8.33.00. Room temperature is kept at 23 with humidity at 50%. Thecrosshead speed is kept constant at 10.00mm/minute and data is sampled at either 5 or 10 pts/second.The lap-shear joint results in the two bonded samples not being in line. When gripped the force fromthe tensile test will therefore not be centred with the bond and this will introduce unnecessary extrarotation to the sample. Metal plates are therefore placed in the grips in order to make sure the sampleis centred as seen in Figure 4.6.

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Figure 4.6: Tensile test setup

The samples are pulled until a break occurs. Once this happens the samples are removed and placedin a plastic bag. Due to a large amount of test samples each batch of samples is averaged. Standarddeviations and all averaged values are found in Appendix 7. The strength is registered in kN and as thebond area is known results are also expressed in pressure(MPa). One thing to keep in mind is that thisassumes that the whole bond area is subjected to an equal force which is not the case as discussed inthe literature study but is still done for easily comparable results.

From the tensile tests the adhesion/cohesion failure is recorded in percentage. This was done by writinga program that segments the bond area into two parts using k-means clustering and then calculatesthe percentage of each part. The program eliminates the subjectivity of estimating and works well forBetamate 1498f as the adhesive is blue. SikaPower 498 that is black/grey is more of a challenge forthe program so this was estimated with visual analysis. Overall the program works well but seems tounderestimate the amount of cohesion failure. A more accurate and efficient program can be achieved ifmore optimisation of the program is done.

FTIR Analysis

Three samples are chosen to perform FTIR analysis on, machine used Varian 7000 with ATR(Attenuatedtotal reflection). Using FTIR identification of oil in the adhesive is determined. Spectrums from pureAnticorit, Renoform and a clean cohesive bond without oil is scanned in order to have references spec-trums for comparison. These spectrums are compared to spectrums from the three samples in order todetermine the presence of oil on the adhesive samples.

4.6 Surface Profile Measurements

The surface profile of the different materials is measured using a Mitutoyo SJ400 and measurements aretaken in the x and y direction of the sheet.

Figure 4.7: Surface profile measurement

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The test sample area was in the centre of the delivered sheet metals prior to cutting. Measurements aretaken in both the transversal and longitudinal direction. The sample area is shown in Figure 4.8 below.

Figure 4.8: Surface sample area

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Chapter 5

Result

5.1 Oil Application

Oil application tests are done for various application techniques. The first batch of tests are done as aninitial test to evaluate the performance of the chosen application methods and storage positions. Resultsfrom the first batch of tests are shown below in Figure 5.1. The dotted line in the graph represents theamount of oil per sample corresponding to 3g/m2.

Figure 5.1: General Testing

From Figure 5.1 it is seen that no method reaches the desired amount of oil. Visual examination ofthe samples showed that when placed horizontal a larger area for the oil to gather at is present whencompared to vertically placed. From Figure 5.1 it is also seen that the samples dipped generate a largeramount of oil compared to samples applied with a household cloth.

Next trail corresponds to application of oil with barcoating rods with six different coating sizes(0-9).Three samples of each coating were evaluated. Results shown in Figure 5.2.

Figure 5.2: Barcoating Application

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Results indicate that barcoating achieve different amounts of oil depending on barcoat number werelarger numbers deposit greater amounts of oil. After four days the amount of oil on all the samplesconverge towards the same amount.

Next batch of tests was on samples applied with household cloth or dipped and with all samples storedvertically. Measurements of the sample weight started and then measured over several days.

Figure 5.3: Oil application by dip and cloth

From Figure 5.3 is can be seen that there is a difference in the amount of oil deposited by dip and cloth.Dipped deposit roughly three times as much oil as cloth but converge to roughly the same amount of oilalready after one day when placed in vertical position.

Next batch were samples coated with barcoat size(Nr. 0), sponge, cloth or dipped. The samples wereweighed and then a paper was placed on the surface to remove oil. The samples were then weighed again.This process was repeated once. The test was performed on the same day in order to minimize the effectof runoff. Measurements were performed again after 3 days. The results are shown in Figure 5.4.

Figure 5.4: Oil removed by paper

It is seen that dipping deposits the largest amount of oil and that cloth/barcoat/sponge deliver approx-imately the same amount.

The last batch was oil applied using a kitchen cloth and three different types of oils; Renoform 3802,Anticorit 4107 and Aral Ropa in order to see if there is any significant difference between the oils interms of application.

Figure 5.5: Different oils and removal by paper

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Coating with Aral Ropa results in an oil amount lower than the desired whilst Anticorit and Renoformperform similarly.

5.1.1 Amount of oil applied

During evaluation of application techniques the amount of oil per samples was checked this includessamples subjected to lap-shear tests. When comparing the application techniques there is a differencein the amount of oil on the samples for each technique. The average and standard deviation of thesemeasurements are shown in Table 5.1 below. To keep in mind is that for barcoating the different rodshave been summarised as one. Cloth has a larger number of samples due to that it includes the samplesfor lap-shear tests. The results below are measurements taken before paper has been used to removeexcess oil.

Application Dip Cloth Sponge BarcoatOil [mg] 61 14 50 48

St.Dev [mg] 31 6 6 14Nr. Samples 14 192 3 21

Table 5.1: Applied oil per method with standard deviation and number of samples per method

5.2 UVF Results

Analysis of the topography and the oil distribution on the surface was performed using Ultra VioletFlorescence(UVF). The analysis method is time consuming and thus only a part of each sample hasbeen analysed. The program outputs the intensity results as negative numbers, a larger absolute valueof the negative number corresponds to a higher intensity. A test was performed on a cleaned and a notcleaned sample were the results can be seen in Figure 5.6. For a sample cleaned according to steps inthe experimental chapter the intensity variations are very small compared to a sample that has not beencleaned in any way.

(a) Clean (b) Not Clean

Figure 5.6: Clean vs not clean sample

Different sizes of the barcoat rods were tested (sizes:0,1,2,3,6,9) with three samples for each barcoat size.After application the samples were stored vertically. The results from barcoat Nr.3 are shown in Figure5.7 below.

(a) C31 (b) C32 (c) C33

Figure 5.7: UVF analysis of oil coated on three samples with barcoat Nr. 3

In the Figures above the left part of the samples show a higher intensity that declines towards the right.

In order to see how removal of excess oil by paper affects the surface UVF scans was taken after oilapplication and then after removal of oil by paper. During this testing the samples were stored vertically.One samples scanned is shown in Figure 5.8

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(a) Anticorit (b) Anticorit after paper

Figure 5.8: Anticorit application by cloth, a) before and b) after removal of oil by paper

After removal of excess oil by paper surface does not have the clearly defined gradient resulting fromrunoff. UVF results for all barcoated samples are found in Appendix A.

5.3 NIR Analysis

NIR analysis is done as a means to quickly analyse whole samples. The method is faster and analysisa larger area than UVF. With a faster method for analysing the oil the affect of how the oil flows afterapplication can be done.

Oil is applied using a cloth, the samples are placed flatly and then immediately scanned. After 15 minutesthe samples are scanned again. The color of the samples do not represent any intensity or value theyare only visual aids working as a form of contrast to clearly see the surface. The samples are shown inFigures 5.9a and 5.9b below.

(a) Sample A afterapplication

(b) Sample B afterapplication

Figure 5.9: Samples directly after application

The samples in Figure 5.9 show distinct lines deriving from the cloth used for application. Scans done15 minutes later are shown below.

(a) Sample A after 15min (b) Sample B after 15min

Figure 5.10: Samples 15min after application

Compared with samples in Figure 5.9 samples in Figure 5.10 do not show as distinct oil lines from thecloth. The vertical line represents a dead pixel in the equipment.

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5.4 Tensile Tests

Lap-shear tests were performed on all bonded samples. Figures of all the results are found in AppendixB including a sheet comprising the strength, average strength , standard deviations for all the lap-sheartests. The tests were performed using an Instron 5566 with software Instron Series IX. The crossheadspeed was set to 10mm/minute with a loadcell of 10kN , load threshold is set to 0.1kN with a load limitof 9.5kN . The test samples had a width of 25mm with a gauge length of 60mm and a grip distance of60mm. The thickness of each sample was measured prior to testing. Five clean samples without oil havebeen tested for each material as part of reference tests. Shown below is the results for the HDG samplesbonded with Betamate 1496f. The legend in the upper left corner contains the amount of oil in g/m2 persample(two samples to each lap sheer sample). The dotted lines are the samples that have been coatedwith a larger amount of oil.

(a) Reference

(b) Anticorit 3802

(c) Renoform 3802

Figure 5.11: HDG Samples bonded with Betamate 1496f

Results show that the strength of the samples do not differ that much with an exception for Anticorit.In the same way Figure 5.12 below show the results for HDG bonded with SikaPower 498.

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(a) Reference

(b) Anticorit 3802

(c) Renoform 3802

Figure 5.12: HDG Samples bonded with SikaPower 498

The results in terms of strength do not differ that much between the different combinations of samples.

Analysing all the samples using the program described in the experimental section the percentage adhe-sive/cohesive failure is determined. The results shown below are averaged results irrespective of amountof oil. The complete results are found in Appendix A.

% Beta/Ref Sika/Ref Beta/Anti Sika/Anti Beta/Reno Sika/RenoHDG 67 56 95 62 91 91ZE 64 95 49 93 40 95

ZnMg 58 61 54 49 58 58AlSi NA NA NA NA NA NA

Table 5.2: Average cohesive failure percentage irrespective of amount of oil

AlSi do not have any results due to delamination between coating and substrate for all samples.

5.4.1 Roughness Measurements

Four measurements were taken for each coating with two samples in the longitudinal and two in thetransversal. The values are calculated as Ra.

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Figure 5.13: Roughness measurements, Ra

Results show that AlSi display the highest surface roughness and HDG the lowest.

5.4.2 FTIR Scans

FTIR scans are done on a few samples in order to detect the presence of oil or adhesive on different partsof the bond area. Comparing samples with or without and scans of only oil a comparison between thescans can be done. Based on the differences/similarity conclusions of where oil i present can be done.Scans are taken on HDG samples that show adhesive or cohesive failure.

(a) Renofrom 7g

(b) Renofrom 7g multiple

(c) Anticorit 3g

Figure 5.14: FTIR scans with scan area and comparison of wavelength peaks

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Chapter 6

Discussion

6.1 Oil Application

Various application techniques have been evaluated with respect to ease of application, amount of oilapplied and oilfilm thickness uniformity. Techniques that have been evaluated were cloth, sponge, bar-coat, dip and spray. Spray was briefly tested but the device available was not capable of dispersing theoil in a spray cloud so this method has not been further investigated. However usage of more powerfulspray dispensers such as electrical powered might work better. Evaluation of the oil application was donethrough weighing of samples and surface analysing techniques such as UVF and NIR. In terms of easeof application cloth and sponge performed well. Applying oil to the sponge or cloth and coating of thesamples was an easy and fast application technique. Barcoating requires rods and a flat even surface.It is also operator dependent as a user with a good technique and/or experience will probably achieve amore precise and controlled coating. One other challenge with barcoating was the width of the samplevs the length of the rod. The sample has a width of 25mm vs the rods length at 300mm, applying anequal pressure over the sample with such a long rod was challenging. Problems with scraping sampleswere also present. Dipping the samples also included some challenges such as making sure that only oneside of the sample was fully coated allowing no oil to spread to the sides or on top of the sample.

From weighing the sample pieces before and after application the weight of the applied oil can bedetermined and thus the performance of the application tool. Of the four application methods thosesamples that were dipped show the largest amount of oil as can be seen in Figures 5.1, 5.3, 5.4 and inTable 5.1. Barcoating varies depending on the rod used as seen in Figure 5.2. There is a clear distinctionbetween the barcoat Nr.9 and the finest barcoat (Nr.0). The rest are not that easy to distinguish anddoes not follow the idea of a finer barcoat(smaller number) will deposit a lesser amount of oil. Thiscan be due to multiple reasons such as poor operating technique whilst coating, viscosity of fluid, theratio of the small width of sample to the bars length resulting in an uneven distribution on the sample.Repeatability was also an issue as applying the same pressure and speed for each application was notthat easy. Hence barcoating seems to be very operator dependent and maybe not be optimal for fluidswith a low viscosity. As seen in Table 5.2 sponge and barcoat both apply roughly the same amount ofoil on average whilst cloth and sponge share the same deviation but cloth applying a smaller amount.Dip and barcoat that are more complicated techniques show a larger standard deviation as compared tothe more easily applied cloth and sponge techniques. This indicating that with the easier methods oneshould be able to achieve more consistent results.

The storage position for most samples were vertical as shown in Figure 4.2a. After application of oilthere is an excess amount on the surface and there is a runoff due to gravity. This runoff leads to less oilon the sample but also an accumulation of oil along the lower edge of the sample. Storing as in Figure4.2a will therefore result in a smaller amount of oil along the lower edge when compared to the storageposition as in Figure 4.2b, hence vertical storage allows more oil to run off. Samples have also been oiledand placed flat on a surface in order to see if there has been any evaporation of the oil. No significantamount of oil is determined to be removed from the surface due to evaporation. However excess oilsimply runs of over the edges.

By weighing samples over several days and comparing the data the transient effect on the samples(due to

24

run off) were determined, this can be seen in Figure 5.3. The amount declined rapidly after the first twodays but for the remaining days the amount declined very little and all the samples reached roughly thesame amount independently of the application technique. The behaviour can be seen in Figure 5.2 and5.3. From this it can be concluded that the choice of application technique may not be that important ifthe samples can be stored for a couple of days prior to usage. However if the sample must be used rightaway the application method will matter. From Figure 5.3 it can be seen that none of the methods byitself will reach the accepted level of oil at 3g/m2. Paper(kleenex) was therefore used to remove excessoil. The paper was lightly pressed on the sample and then carefully removed without wiping the surface.From Figure 5.3 it is seen that the use of paper removes oil and after two iterations of this the samplesapplied by barcoat and cloth have reached an oil level below the required. The samples that are dippedand two of the sponge samples did not reach the accepted level. As a second step the samples werestored vertically and weighed after three days. It was shown that the oil amount had declined and wasalmost at the required level for all the samples. From the above it is seen that there is a transient factorto the run off of oil and that paper is an effective way to immidietly reach an acceptable amount of oil.

An overall examination on all the UVF samples show a recurring pattern, the oil distribution is seento be distributed unevenly as a gradient with lower intensities on the right part of the samples. Thisarea corresponds to higher up on the scan area. The gradient is most prominent in the samples with oilapplied with barcoat. The gradient derives from the vertical storage position of the samples resulting inexcess oil flowing down the samples. Scanned samples before and after removal of oil by paper do notas clearly display the gradient as seen in Figure 5.8. The paper removes oil and in the process seems toremove any areas with a larger distribution creating a more uniform surface. From this it can be seenthat using a paper as removal method can help remove gradients on the sample.

Near infra-red(NIR) scanning was briefly used to analyse two samples coated with oil. Whilst UVFscanning took roughly 15minutes to scan 10cm2 the NIR scan took roughly 10 − 15seconds to scanmultiple samples and the whole sample area. This made it possible to view the oil surface directlyafter application. As seen in Figure 5.9 immediately after application oil lines from the cloth are clearlydefined. The presence of oil lines is not wanted so another scan was done after 15 minutes with thesamples resting flat to see if any change can be seen. Performing the same scan the lines have diminishedas seen in Figure 5.10. Letting the samples rest will thus allow the oil to flow out creating a more uniformoil film thickness.

From the scans and application tests a routine for application of oil is developed. The routine is shownstep by step below.

1. Weighing of sample.

2. Application of oil to sample using cloth.

3. Samples stored vertically.

4. Weighing of samples.

Excess oil removed with paper or more oil added with cloth, repeat if needed

5. Place samples on flat surface for 1 hour before application of adhesive

Cleaning of the samples are done according to the steps described in Chapter 4.

6.2 Lap Shear Tests

Lap shear tests have been done to test the adhesion and bond strength of HDG, EG, AlSi and ZnMgsamples. The impact of different adhesives and oils have been studied. The lap shear tests done giveinformation about the strength of the bond joint and how large of the area that is adhesive respectivelycohesive.

Due to the materials having different thickness comparison between the bond strength for the materialsshould be done with caution, AlSi having boron steel resulting in a very high strength steel comparedto electrogalvanised and ZnMg having a thickness of 0.8mm will display different bond strengths withAlSi having the greatest. HDG with a thickness of 1.5mm will be somewhere in-between. The changein strength depends on the thicker or high strength samples having better resistance towards rotationunder tension thus minimizing bending and the stresses on the bond.

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Any values presented below in parenthesis represent the standard deviation of the whole sample popu-lation for that combination of amount of oil/adhesive/coating.

6.2.1 HDG

Examining the strength of all the different combinations there does not seem to be any drop in strengthfor samples coated with different amounts of oil, type of oil or adhesive. The only exception to this is thecase of Betamate 1496f with Anticorit 3802. These samples show relatively large variations in strengthwith standard deviations at about 8MPa. Looking at the results for the failure mode it is seen thatSikaPower 498 performs better than Betamate 1496f. From further examination of the cohesive failureresults for Betamate in combination with Anticorit there is seen that these show a low cohesive failurepercentage with a high standard deviation of 28%. The combination of Betamate 1496f, Anticorit 3802and HDG do not seem to work well together and the cause is still unknown.

Examining the bond strengths it is seen that roughly the same strength values are reached but with adifference in the amount of cohesive failure. Betamate 1496f samples with a lower amount of cohesivefailure exhibit the same strength as SikaPower 498 samples with higher cohesive failure. Also visuallyexamining the samples Betamate 1496f show a more prominent adhesive failure zone at the edge of thesamples, Sika does not have this clear boundary. FTIR scans of cohesive failure area on a Betamate1496f/Renoform 3802 sample with 7g of oil show no oil present in the cohesive area indicating that nooil has been absorbed. To keep in mind is that the scans with ATR only penetrates roughly 0.5µm intothe surface. Hence oil might be present under the top most layer of the adhesive. If there is oil presentin the adhesive under the top layer this does not seem to affect the strength of the adhesive as the crackpropagation path has gone through an area of adhesive that shows no presence of oil instead of havinga path through a region with oil.

FTIR scans show that at areas with adhesive failure oil is present at the interface region between theadhesive and its coating whilst in cohesive failure no oil is present. This can help explain why someof the Betamate 1496f and Anticorit 3802 samples display a low strength; The oil present may form athin layer between adhesive and coating resulting in low intermolecular bonds forming giving rise to lowstrength. The more prominent adhesive failure at the boundaries may also be caused by this presenceof oil at the boundaries.

6.2.2 Electro galvanised

The electro galvanised samples have an average strength for all the samples at 17.53(0.36)MPa. Thestandard deviation is very low so there is essentially no difference in bond strength between any of thesamples, they all perform equally. The failure percentage of the bond surface follows the same patternas HDG samples with SikaPower 498 achieving a higher degree of cohesive failure compared to Betamate1496f samples.

For electro galvanised samples there is also be seen a difference in cohesive failure percentage relating tothe amount of oil. This relation between oil amount and failure is only seen for Betamate 1496f sampleswith highest cohesive failure for reference and lowest for 7g of oil with 3g in the middle. The largestspread in the results are also found for bonds with the highest amount of oil. This result that shows adifference in cohesive failure between the amount of oil is not present for the HDG samples indicatingthat electro galvanised samples may be more sensitive to changes in the amount of oil.

6.2.3 ZnMg

ZnMg samples have an average strength of 17.82(0.24)MPa for all samples. As with electro galvanisedsamples ZnMg displays a very low spread in strength implying that the strength is independent of theamount of oil applied and the type of adhesive used. The thickness of the samples are the same as forelectro galvanised and the strength of the bonds are also essentially equal. The cohesive failure for allsamples is at 54% with a standard deviation of 4%. The results indicating that the cohesive failure isnot dependent on the amount of oil or adhesive.

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6.2.4 AlSi

Due to delamination of the coating from the substrate the adhesive strength of the bond has not beenable to be determined, delamination took place at an average stress of 34(3)MPa. Cohesive failure couldnot be determined for the same reason. Delamination taking place at such high stresses(relative to othersamples) with the adhesive bond holding indicates that the adhesive strength can actually carry a largerload than the loads determined for the other materials. This is most likely due to the thickness andmechanical properties of the AlSi samples. The substrate is boron steel and the total thickness of thesample is 1.1mm resulting in a very strong material with good resistance to bending. These samples arebetter described by the bending in Figure 6.1a with no rotation whilst the other materials more resemblethe lap shear tests in Figure 6.1b.

(a) No rotation under tensile load (b) Rotation under tensile load

Figure 6.1: Load distribution under tensile load

6.3 Material Impact on joint strength discussion

From the results and discussion above it is clear that the different materials have shown different mechan-ical and failure properties. Internally between the same material results have for most cases been veryconsistent. The weakest materials in terms of bond strength is electro galvanised and ZnMg. What theyhave in common is the material thickness of 0.8mm. The low thickness results in bending of the samplesduring testing. Comparing the samples in Figure 6.2 below there can be seen that electro galvanisedand ZnMg show the largest amount of bending followed by HDG and lastly AlSi that does not show anysigns of deformation.

Figure 6.2: Deformation of samples

HDG has the largest thickness at 1.5mm whilst AlSi is at 1.1mm but as AlSi is a boron steel its strengthis much higher giving it a better flexural rigidity. There is also a slight creation of a neck in the thinnersamples in the area before the adhesive bond, for HDG and AlSi this is not present. From the bendingof the samples it is shown that having materials of higher strength steel or thicker samples will minimizerotation increasing the amount of stress the adhesive bond can carry.

6.4 Adhesive Properties and handling

According to product specification the amount of oil the adhesives have been designed to handle was2g for SikaPower 498 and 4g for Betamate 1496f. The bonded samples have had been applied with oilhaving a larger quantity than 2g and half of the samples with a higher amount than 4g. From the resultsthese values do not seem to reflect the actual amount of oil the adhesives can handle in terms of strength.It is also not specified in the product sheet at to what characteristic this maximum amount of oil relatesto, if it affects the bond strength, handling or adhesion but based on the tests done both adhesives areable to handle more than specified.

The adhesives properties differed in terms of application settings. Betamate worked best at an applicationtemperature of 60whilst SikaPower 498 was applied at 55. Even though Betamate 1496f had an higherapplication temperature its viscosity was higher making it more demanding to apply and the pressureneeded to be set to 4bar to achieve a good flow. SikaPower 498 on the other hand only needed a pressureat around 2.3bar to achieve the same flow as Betamate 1496f. Application of the adhesives to clean

27

metal was not a problem as both adhered to the surface. With the application of 3g of oil Betamate1496f had some problems adhering to the surface and was prone to sliding around on the oil film. WhereSikaPower 498 had a better resilience to sliding at this amount of oil but still did not adhere as well asthe clean samples. However at 7g of oil both samples had problems adhering but even here SikaPower498 performed better than Betamate 1496f. This problem with adherence indicates that the oil filmforms a layer between the substrate and the adhesive and that the oil is not immediately absorbed bythe adhesive.

Once applied when fixing the samples with screws the adhesive will flow out towards the sides as theadhesive is applied along the centre of the area. This flow might have caused the oil to be pushed outtowards the edges resulting in a higher amount of oil along the edges. If this is the case it may be afactor as to why there is mostly adhesive failure at the leading edge as seen in Figure 6.3 below. Theexcess amount of oil transferred to the edges may be to much for the adhesive to handle resulting inadhesive failure. In general Betamate 1496f samples showed a more prominent adhesive failure zone atthe edges and if there is a larger amount of oil located here this can indicate the Betamate 1496f has aharder time dealing with the larger quantity of oil than SikaPower 498 has.

Figure 6.3: ZnMg samples with 7g of oil

An interesting detail when comparing the adhesive is that both display roughly the same strengththroughout the tests but show different degrees of failure mode. Betamate 1496f have larger adhesivesfailure areas but the same strength as SikaPower 498. Cohesive failure is often more favourable as theadhesive has adhered to the surface indicating good adhesion and a correct surface to bond to. Adhesivefailure is at an interface and indicates the surface properties are inadequate and something has to bedone to the surface.

6.5 Bond geometry

One other factor that could play a part in the starting point of failure is the outflow of adhesive under orover the teflon tape. The adhesive did not bond to the teflon tape and therefore made sure to not provideany extra bonding area for the adhesive. However while making sure that the bond area is fixed thetape can still allow an outflow of adhesive over or under the tape and in that way affect the initial crackpropagation point and a what stress this happens. This is related to the stress concentration factor Kt.Sharp interface points at for examples 90◦ edges will have a Kt factor increasing the chance of failure,shown Figure 6.4a below.

(a) High K factor (b) Low K factor

Figure 6.4: Adhesive outflow on stress concentration

Figure 6.4b describes a more ideal situation as in here we have an outflow of adhesive resulting in a lessprominent edge for the adhesive. The slope lowers the stress concentration point and therefore loweringthe chance of failure starting at the edge when compared to the edge in Figure 6.4a. The samples thathave been tested during this project have all had an outflow of adhesive due to a too large amountapplied inducing outflow of the adhesives which should in theory lower the stress concentration factor.

28

Chapter 7

Conclusion

Development of an oil application technique and lap shear testing of adhesive bonds have been performedduring the project in order to develop an easy way to determine the amount of oil on a sample and thento evaluate the strength och failure mode of adhesives bonds subjected to varying amounts of oil. Theapplication technique developed is found below.

1. Using kitchen roll paper and acetone the samples are wiped to remove dirt and excess oil.

2. The samples are then placed in an ultrasonic bath of acetone for 5min.

3. After the bath the samples are rinsed in a washing bottle filled with acetone and then placed in afixture for drying.

4. The samples are checked and if visual stains are present, the above steps are repeated.

5. Placed in plastic bags until further use.

6. Samples weighed.

7. Oil applied with cloth

Creating oil lines on surface.

8. Samples stored vertically.

Oil run off and creates gradient in oil thickness.

9. Samples weighed.

Excess oil removed with paper placed on surface or if needed more oil is applied.

10. Samples stored vertically.

Oil run off and creates gradient in oil thickness.

11. Samples placed on flat surface at least 1h before application of oil.

Remove gradient.

The above application should result in an amount of oil close to the required. Cloth ensures easy andfast application but creates oil lines. Storage position creates a gradient in the oil film but induces runoff. This non uniform oil distribution is countered by placing the samples flat for at least one hour priorto adhesive application.

Lap shear tests show that the different materials behave differently when compared with each other.Internally between the same material the results are quite coherent independent of amount of oil oradhesive. The exception to this is for HDG with Anticorit and Betamate that seem to be incompatible.The strength of the bond is seen to be independent of adhesive but dependent on the material tobond. High strength materials with high resistance to bending show a better bond strength. Comparingcohesive/adhesive failure percentage it is seen that Sika performs better with a higher degree of cohesivefailure than Betamate but still they achieve the same strength. Analysis of certain points on the bondarea with FTIR locate the oil to be present at the interface region between adhesive and the coatingwhilst no oil is present in the cohesive failure area.

29

Bibliography

[1] Swedish Standard. Adhesives - Terms and definitions SS-EN 923:2005+A1:2008(E). 2008.[2] Lacombe Robert. Adhesion Measurement Methods, Theory and Practice. Florida: CRC Press, 2006.[3] Drew Myers. Surfaces,Interfaces and Colloids, Principles and Applications-Second Edition. USA:

John Wiley & Sons, 1999.[4] Adams R.D. Adhesion Measurement Methods, Theory and Practice. CRC Press, 2006.[5] Lee Lieng-Huang. Adhesive Bonding, Edited. Plenum Press, 1991.[6] Dolk Ake. MG2037 HT14 Industriell limningsteknik, Kompdendium Del 1. 2012.[7] EN ISO 10365:1992-Adhesives-Disignation of main failure patterns. 1992.[8] Brockman W et al. Adhesive Bonding. Material, Applications and Technology. Wiley-VCH, 2009.[9] Bonk Robert B et al. Methods for evaluating adhesive systems and Adhesion. Tech. rep. U.S. Army

Armament Research, Development and Engineering Center, 1996.[10] Maaß Dr.Peter et al. Handbook of Hot-Dip Galvanisation. Wiley-VCH, 2011.[11] Gaillard F et al. Surf,Interface Anal.23, p.307. 1995.[12] Caizhen Yao, Weiwei Chen, and Wei Gao. “Codeposited Zn-Mg coating with improved mechanical

andn anticorrosion properties”. In: Surface & Coatings Technology 219 (2013), pp. 126–130.[13] Monojit Dutta, Arup Kumar Halder, and Shiv Brat Singh. “Morphology and properties of hot dip

Zn-Mg and Zn-Mg-Al alloy coatings on steel sheet”. In: Surface & Coatings Technology 205 (2010),pp. 2578–2584.

[14] Structural bonding of ZnMg-coated steel sheet. Scania. 2012.[15] Fan D.w et al. Materials Science and Technology p.99. 2007.[16] Karbasian H, Tekkaya A.E, and Mater J. Process Technology 210(15) p.2103. 2010.[17] Swerea. Laser induced ultraviolet flourescence. Tech. rep.[18] Adhesives - Determination of tensile lap-shear strength of bonded assemblies SS-EN 1465:2009.

2009.

30

Appendix A

UVF Results

Oil Application by Dip

(a) D1 (b) D2

(c) D3 (d) D4

(e) D5 (f) D6

Figure A.1: Oil application by Dip

31

Oil Application by Cloth

(a) A1 (b) A2

(c) A3 (d) A4

(e) A5 (f) A6

Figure A.2: Oil application by Cloth

32

Oil

Ap

pli

cati

on

by

Barc

oat

(a)

C0

1(b

)C

02

(c)

C0

3

Fig

ure

A.3

:U

VF

an

aly

sis

of

oil

wit

hba

rcoa

tN

r.0

(a)

C1

1(b

)C

12

(c)

C1

3

Fig

ure

A.4

:U

VF

an

aly

sis

of

oil

wit

hba

rcoa

tN

r.1

(a)

C2

1(b

)C

22

(c)

C2

3

Fig

ure

A.5

:U

VF

an

aly

sis

of

oil

wit

hba

rcoa

tN

r.2

33

(a)

C6

1(b

)C

62

(c)

C6

3

Fig

ure

A.6

:U

VF

an

aly

sis

of

oil

wit

hba

rcoa

tN

r.6

(a)

C9

1(b

)C

92

(c)

C9

3

Fig

ure

A.7

:U

VF

an

aly

sis

of

oil

wit

hba

rcoa

tN

r.9

34

Three Types of Oils Applied with Cloth

Oil was applied using a cloth and then scanned, after scanning a paper was applied to the surface andexcess oil was removed. Sample was then scanned again.

(a) Anticorit-AT1 (b) Anticorit-Paper-AT1

(c) Anticorit-AT2 (d) Anticorit-Paper-AT2

(e) Anticorit-AT3 (f) Anticorit-Paper-AT3

Figure A.8: Anticorit application by Cloth, removal by paper

(a) Renoform-RT1 (b) Renoform-Paper-RT1

(c) Renoform-RT2 (d) Renoform-Paper-RT2

(e) Renoform-RT3 (f) Renoform-Paper-RT3

Figure A.9: Renoform application by Cloth, removal by paper

35

Appendix B

Tensile Tests

Betamate 1496

(a) HDG

(b) ZnMg

(c) ZE

(d) AlSi

Figure B.1: Reference Tests-Betamate 1496

36

Anticorit Samples

(a) HDG

(b) ZnMg

(c) ZE

(d) AlSi

Figure B.2: Oiled samples, Betamate 1496 and Anticorit 3802

37

Renoform Samples

(a) HDG

(b) ZnMg

(c) ZE

(d) AlSi

Figure B.3: Oiled Samples, Betamate 1496 and Renofom 3802

38

SikaPower 498

Reference

(a) HDG

(b) ZnMg

(c) ZE

(d) AlSi

Figure B.4: Reference Tests - SikaPower 498

39

Anticorit Samples

(a) HDG

(b) ZnMg

(c) ZE

(d) AlSi

Figure B.5: Oiled samples, SikaPower 498 and Anticorit 3802

40

Renoform Samples

(a) HDG

(b) ZnMg

(c) ZE

(d) AlSi

Figure B.6: Oiled Samples, Betamate 1496 and Renofom 3802

41

Beta Ref Sika Ref Beta/Anti 3g Sika/Anti 3g Beta/Anti 7g Sika/Anti 7g Beta/Reno 3g Sika/Reno 3g Beta/Reno 7g Sika/Reno 7g

Units: kN

HDG: 8,408 8,3526 6,9509 8,1556 7,2985 8,1236 8,3298 8,0571 8,0294 8,0774

8,6259 7,9739 7,2242 8,3329 1,1845 7,8957 8,3401 8,223 8,0073 8,0625

8,4402 8,2947 1,433 8,2139 3,3216 8,1129 8,1558 8,2461 7,7509 8,1291

8,0989 8,2188

8,3256 6,594

Average: 8,3797 7,8868 5,2027 8,2341 3,9349 8,0441 8,2752 8,1754 7,9292 8,0897

St.Dev 0,1714 0,6592 2,6679 0,0738 2,5334 0,1050 0,0846 0,0842 0,1264 0,0285

ZE: 5,6679 5,5765 5,433 5,5257 5,2787 5,4012 5,5712 5,4831 5,3787 5,4253

5,6503 5,5354 5,4166 5,5099 5,2885 5,4366 5,5284 5,6003 5,5029 5,4218

5,6419 5,5062 5,3989 5,3981 5,1988 5,4603 5,3906 5,5413 5,2905 5,4449

5,6169 5,4926

5,6469 5,5469

Average: 5,6448 5,5315 5,4162 5,4779 5,2553 5,4327 5,4967 5,5416 5,3907 5,4307

St.Dev 0,0165 0,0298 0,0139 0,0568 0,0402 0,0243 0,0771 0,0478 0,0871 0,0102

ZnMg: 5,6022 5,5486 5,4761 5,6684 5,6092 5,6028 5,4585 5,4409 5,4737 5,6324

5,6386 5,6703 5,5353 5,6252 5,5871 5,5693 5,5823 5,6539 5,429 5,6107

5,5592 5,6814 5,5066 5,6208 5,4719 5,6653 5,5529 5,5635 5,4288 5,5986

5,4595 5,6499

5,5606 5,5898

Average: 5,5640 5,6280 5,5060 5,6381 5,5561 5,6125 5,5312 5,5528 5,4438 5,6139

St.Dev 0,0600 0,0508 0,0242 0,0215 0,0602 0,0398 0,0528 0,0873 0,0211 0,0140

Tensile Data

42

Adhesive/Cohesive Failure Percentage

% Cohesive

HDG: Beta/Ref Sika/Ref Beta/Anti Sika/Anti Beta/Reno Sika/Reno Beta/Anti 3g Beta/Anti 7g Beta/Reno 3g Beta/Reno 7g

66 95 56 95 61 90 56 67 61 63

69 90 59 95 61 95 59 5 61 62

71 90 5 95 58 85 5 15 58 65

59 95 67 85 63 90

69 * 5 95 62 90

15 95 65 95

Average: 67 93 35 93 62 91 40 29 60 63

ST.dev 4 3 28 4 2 3 25 27 1 1

ZE: 58 95 52 90 44 95 52 24 44 18

62 95 53 90 51 95 53 55 51 50

69 95 57 95 48 95 57 54 48 30

58 95 24 95 18 95

64 95 55 90 50 95

54 95 30 95

Average: 62 95 49 93 40 95 54 44 48 33

ST.Dev 4 0 12 2 12 0 2 14 3 13

ZnMg: 59 67 57 53 52 66 57 46 52 44

56 63 55 55 53 62 55 66 53 45

56 59 53 59 53 58 53 48 53 44

64 60 46 52 44 55

53 58 66 55 45 49

48 50 44 60

Average: 58 61 54 54 49 58 55 53 53 44

ST.dev 4 3 6 2 4 6 2 9 0 0

AlSi: NA-Delamination of coating *-Bond Area not fully coated

Cohesive Percent

43

Appendix C

Adhesive Bond-SikaPower 498

Several photos of the bond area for different combinations of oil and substrate bonded with SikaPower498 are shown below.

HDG Reference

(a) 1 (b) 2

Figure C.1: Reference Tests-HDG Sika

HDG Anticorit 3802

(a) 1 (b) 2

(c) 3

Figure C.2: Anticorit,HDG Sika

HDG Renoform 3802

(a) 1 (b) 2

(c) 3

Figure C.3: Renoform,HDG Sika

44

ZE Reference

(a) 1 (b) 2

Figure C.4: Reference Tests-ZE Sika

ZE Anticorit 3802

(a) 1 (b) 2

(c) 3

Figure C.5: Anticorit,HDG Sika

ZE Renoform 3802

(a) 1 (b) 2

(c) 3

Figure C.6: Renoform,ZE Sika

45

ZnMg Reference

(a) 1 (b) 2

(c) 3

Figure C.7: Reference Tests-ZnMg Sika

ZnMg Anticorit 3802

(a) 1 (b) 2

(c) 3

Figure C.8: Anticorit,ZnMg Sika

ZnMg Renoform 3802

(a) 1 (b) 2

(c) 3

Figure C.9: Renoform,ZnMg Sika

46

AlSi Reference

(a) 1 (b) 2

(c) 3

Figure C.10: Reference, AlSi Sika

AlSi Anticorit 3802

(a) 1 (b) 2

(c) 3

Figure C.11: Anticorit 3802, AlSi Sika

AlSi Renoform 3802

(a) 1 (b) 2

(c) 3

Figure C.12: Renoform 3802, AlSi Sika

47

Appendix D

Adhesive Bond-Betamate 1496

Several photos of the bond area for different combinations of oil and substrate bonded with Betamate1496 are shown below.

HDG Reference

(a) 1 (b) 2

(c) 3

Figure D.1: Reference Tests-HDG Betamate

HDG Anticorit 3802

(a) 1 (b) 2

(c) 3

Figure D.2: Anticorit,HDG Betamate

48

HDG Renoform 3802

(a) 1 (b) 2

(c) 3

Figure D.3: Renoform ,HDG Betamate

ZE Reference

(a) 1 (b) 2

(c) 3

Figure D.4: Reference Tests-ZE Betamate

ZE Anticorit 3802

(a) 1 (b) 2

(c) 3

Figure D.5: Anticorit,ZE Betamate

49

ZE Renoform 3802

(a) 1 (b) 2

(c) 3

Figure D.6: Renoform,ZE Betamate

ZnMg Reference

(a) 1 (b) 2

(c) 3

Figure D.7: Reference Tests-ZnMg Betamate

ZnMg Anticorit 3802

(a) 1 (b) 2

(c) 3

Figure D.8: Anticorit,ZnMg Betamate

50

ZnMg Renoform 3802

(a) 1 (b) 2

(c) 3

Figure D.9: Renoform,ZnMg Betamate

AlSi Reference

(a) 1 (b) 2

(c) 3

Figure D.10: Reference, AlSi Betamate

AlSi Anticorit 3802

(a) 1 (b) 2

(c) 3

Figure D.11: Anticorit 3802, AlSi Betamate

51

AlSi Renoform 3802

(a) 1 (b) 2

(c) 3

Figure D.12: Renoform 3802, AlSi Betamate

52

IntroductionLiterature StudyAdhesion TheorySpecific adhesionMechanical AdhesionThermodynamic Work of Adhesion

Surface Characteristics Affecting AdhesionSurface Energy and its MeasurementWettingSurface Roughness

Adhesive Bonds and Test MethodsAdhesive Failure ModesPeel TestLap-shear Test

CoatingsGalvanized SteelZnMg Coated SteelAlSi Coated Steel

Oil AnalysisSpectroscopy

Surface Roughness Analysis

MaterialOilsAdhesivesSheet Material

ExperimentalOil ApplicationSample Size and PreparationSurface Treatment Prior to Oil ApplicationCleaning of Sheet Metal SpecimensOil Application and MeasurementOil Analysis of oil distribution and amount of oilWeighingUVF-Spectroscopy NIR-spectroscopy

Adhesion TestingSample Size and PreparationSurface Treatment prior to bondingAdhesive Application and CuringBonding AssemblyAdhesive ApplicationCuring

Surface Profile Measurements

ResultOil ApplicationAmount of oil applied

UVF ResultsNIR AnalysisTensile TestsRoughness MeasurementsFTIR Scans

DiscussionOil ApplicationLap Shear TestsHDGElectro galvanisedZnMgAlSi

Material Impact on joint strength discussionAdhesive Properties and handlingBond geometry

ConclusionAppendix UVF ResultsAppendix Tensile TestsAppendix Adhesive Bond-SikaPower 498Appendix Adhesive Bond-Betamate 1496