baqir.ppt
TRANSCRIPT
In this paper, we will study the corrosion resistance of aluminum after adding it a few additions of copper
At the outset, we should learn to aluminum and copper up close and learn about their characteristics and also identify the corrosion and what we mean by it.
AluminiumGeneral Characteristics of Aluminium
• Is a chemical element in the boron group with symbol Al and atomic number 13. It is a silvery white, soft, ductile metal. Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal in the Earth's crust. It makes up about 8% by weight of the Earth’s solid surface. Aluminium metal is so chemically
reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals.[11] The chief ore of aluminium is bauxite.
•Aluminium is remarkable for the metal’s low density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and
•structural materials. The most useful compounds of aluminium, at least on a weight basis, are the oxides and sulfates [12].
CopperGeneral Characteristics of Copper:
•Copper has chemical element with symbol Cu (from Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity.
•Pure copper is soft and malleable; a freshly exposed surface has a reddish-orange color. It is used as a conductor of heat and electricity, a building material, and a constituent of various metal alloys. The metal and its alloys have been used for thousands of years. In the Roman era, copper was principally mined on Cyprus, hence the origin of the name of the metal as сyprium (metal of Cyprus), later shortened to сuprum.
•Its compounds are commonly encountered as copper(II) salts, which often impart blue or green colors to minerals such as azurite and turquoise and have been widely used historically as pigments. Architectural structures built with copper corrode to give green verdigris (or patina). Decorative art prominently features copper, both by itself and as part of pigments. Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase. In molluscs and crustacea copper is a constituent of the blood pigment hemocyanin, which is replaced by the iron-complexed hemoglobin in fish and other vertebrates. The main areas where copper is found in humans are
•liver, muscle and bone[51] . Copper compounds are used as bacteriostatic substances, fungicides, and wood preservatives.
Corrosion
•has 2 senses: CORROSION. 1-a state of deterioration in metals caused by
oxidation or chemical action
. erosion by chemical action -2
The breaking down or destruction of a material, especially a metal, through chemical reactions. The most common form of corrosion is rusting, which occurs when iron combines with oxygen
and water .
Corrosion comes in many different forms and can be classified by the cause of the chemical deterioration of a metal. Listed below are 10 common types of corrosion:
• . 1 General Attack Corrosion Also known as uniform attack corrosion, general attack corrosion is the most common type of corrosion and is caused by a chemical or electrochemical reaction that results in the deterioration of the entire exposed surface of a metal. Ultimately, the metal deteriorates to the point of failure.
• General attack corrosion accounts for the greatest amount of metal destruction by corrosion, but is considered as a safe form of corrosion, due to the fact that it is predictable, manageable and often preventable.
• .2 Localized Corrosion Unlike general attack corrosion, localized corrosion specifically targets one area of the metal structure. Localized corrosion is classified as one of three types:
• Pitting: Pitting results when a small hole, or cavity, forms in the metal, usually as a result of de-passivation of a small area. This area becomes anodic, while part of the remaining metal becomes cathodic, producing a localized galvanic reaction. The deterioration of this small area penetrates the metal and can lead to failure. This form of corrosion is often difficult to detect due to the fact that it is usually relatively small and may be covered and hidden by corrosion-produced compounds
• Crevice corrosion: Similar to pitting, crevice corrosion occurs at a specific location. This type of corrosion is often associated with a stagnant micro-environment, like those found under gaskets and washers and clamps. Acidic conditions, or a depletion of oxygen in a crevice can lead to crevice corrosion.
• Filiform corrosion: Occurring under painted or plated surfaces when water breaches the coating, filiform corrosion begins at small defects in the coating and spreads to cause structural weakness.
• . 3 Galvanic Corrosion:Galvanic corrosion, or dissimiliar metal corrosion, occurs when two different metals are located together in a corrosive electrolyte. A galvanic couple forms between the two metals, where one metal becomes the anode and the other the cathode. The anode, or sacrificial metal, corrodes and deteriorates faster than it would alone, while the cathode deteriorates more slowly than it would otherwise.
• Three conditions must exist for galvanic corrosion to occur:
• Electrochemically dissimilar metals must be present
• The metals must be in electrical contact, and
• The metals must be exposed to an electrolyte
• . 4 Environmental Cracking:Environmental cracking is a corrosion process that can result from a combination of environmental conditions affecting the metal. Chemical, temperature and stress-related conditions can result in the following types of environmental corrosion:
• Stress Corrosion Cracking (SCC) • Corrosion fatigue • Hydrogen-induced cracking • Liquid metal embrittlement
• . 5 Flow-Assisted Corrosion (FAC):Flow-assisted corrosion, or flow-accelerated corrosion, results when a protective layer of oxide on a metal surface is dissolved or removed by wind or water, exposing the underlying metal to further corrode and deteriorate.
• Erosion-assisted corrosion
• Impingement
• Cavitation
• . 7 Intergranular corrosionIntergranular corrosion is a chemical or electrochemical attack on the grain boundaries of a metal. This often occurs due to impurities in the metal, which tend to be present in higher contents near grain boundaries. These boundaries can be more vulnerable to corrosion than the bulk of the metal.
• . 8 De-Alloying:De-alloying, or selective leaching, is the selective corrosion of a specific element in an alloy. The most common type of de-alloying is de-zincification of unstabilized brass. The result of corrosion in such cases is a deteriorated and porous copper
• . 9 Fretting corrosion:Fretting corrosion occurs as a result of repeated wearing, weight and/or vibration on an uneven, rough surface. Corrosion, resulting in pits and grooves, occurs on the surface. Fretting corrosion is often found in rotation and impact machinery, bolted assemblies and bearings, as well as to surfaces exposed to vibration during transportation
• . 10 High-Temperature Corrosion:Fuels used in gas turbines, diesel engines and other machinery, which contain vanadium or sulfates can, during combustion, form compounds with a low melting point. These compounds are very corrosive towards metal alloys normally resistant to high temperatures and corrosion, including stainless steel.
• High temperature corrosion can also be caused by high temperature oxidization, sulfidation and carbonization.
• •1.1 -Definition of Corrosion
•Corrosion may be defined as a destructive phenomena, chemical or electrochemical, which can attack any metal or alloy through reaction by the surrounding environment and in extreme cases may cause structural failure. Corrosion can be also defined as the deterioration of material by reaction to its environment. The corrosion occurs because of the natural tendency for most metals to return to their natural state; e.g., iron in the presence of moist air will revert to its natural state, iron oxide. Metals can be corroded by the direct reaction of the metal to a chemical; e.g., zinc will react with dilute sulfuric acid, and magnesium will react with alcohols .
Types of Corrosion
•Corrosion does not only occur as linear abrasion, but in versatile forms of appearance.
•According to DIN EN ISO 8044, important variants for unalloyed or alloyed
•steel are:
•1-Uniform surface corrosion•General corrosion occurring on the entire surface at
nearly the same•rate.
•2 -Shallow pit corrosion•Corrosion with locally different abrasion rates; caused by
the existence of corrosion•elements.
•3 -Pitting corrosion•Local corrosion resulting in holes, that is, in cavities
expanding from the•surface to the inside of the metal.
•4-Crevice corrosion•Local corrosion in connection with crevices occurring in or
immediately adjacent•to the crevice area, which has developed between the metal surface
and•another surface (metal or nonmetal).
•5 -Contact corrosion (aka dissimilar metal corrosion)•Occurs at contact surfaces of different metals; the acceleratedly
corroding metal•area is the anode of the corrosion element.
•6 -Intergranular corrosion•Corrosion in or adjacent to the grain boundaries of a metal.
•The standard mentioned above describes altogether 37 types of corrosion. These
•types of corrosion result in corrosion phenomena.
Experimental part
•Casting materials•Different samples of AL-Cu Alloys,were used in
this work.The base material used throughout this work was the commercial pure Aluminum of 99.9%wt Al,pure copper with 99,9% purity was used as an alloying element, which have melting point temperature (1083C) and density of (8.2g/cm^2) at (20C) six alloys with different weight percentage copper were prepared, i.e.1,2,3,4.5 and 6%wt Cu.
Equipment and Experimental
•The following machines and equipments were used:
•a.Sensitive balance device three digits
•b. Electrical furnace
•c. Digital camera
•d. Micro structure tester
Manufacturing Alloys by Casting
•The Aluminum Copper Metals Have (99.9%) purity.The Manufacturing of Sample was by Gravity Casting Procedure:
•1(Weighing the alloying elements by using sensitive balance with accuracy (0.001mg).
•2(Using an electrical furnace,the melting procedure was firstly performed by melting aluminum, using graphite crucible which was preheated in the furnace then the addition of copper element was carried out at (750c)
•3(During the addition of copper to the molten aluminum manual stirring with graphite rod with diameter (2.5cm) was applied carefully to avoid producing too much dross.
•4 (Pouring the molten alloys to a steel mould shown ,in fig (6), and the steel casting mold dimension is shown in figure (7), then leaving the casting to cool to the room temperature and using a digital camera to record the temperature readings,because of difficulty of recording the temperature drop in the start of casting alloys.
•5 (Six casting of aluminum-copper were manufactured with different addition.the preliminary chemical composition is given in table (1)
Corrosion media
•After prepare the specimens marked to recognize one from another with putting cables with different colors
•To media used to corrosion test in this work
•1 -Acidic media : sex sample with different percentages of copper were imerrsion in (H2SO4) media with PH=2 by dilute it with distilled water
•2 -BASICAL MEDIA: sex sample with different percentages of copper were imerrsion in (NAOH) media with PH=12 by dilute it with distilled water
PROCEDURE OF CORROSION TEST
•A- specification of the device parts the following device which is shown below was used to test the corrosion rate of the samples which were used in this work
•1 -for acidic test:•b-mechanisim of the device working
•We put(PH) meter in the solution which is contained from concentrated (H2SO4) and distilled water until the (PH) meter reads or reaches equal to 2,continously stirred.
•2 -for basic test:• We put(PH) meter in the solution which is
contained from concentrated (NAOH) and distilled water until the (PH) meter reads or reaches equal to 12,continously stirred.
•After the above steps we setting the device as shwon the diagram of fig. below
•The following steps were followed to taking data:•1 -we put the sample in the beaker which contain either
acidic or basic media•2 -the calomel must put in the burette with putting the
same solution due to the corrosion test case•3 -the space between the sample and the nozzle of the
calomel must be not increase from (2mm) to neglate the resistance of the solution, be the reading of the resistance just of the sample
•4 -after the setting all things we starting the device by power supply and setting ameter and voltmeter and taking the data
Voltage
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the specimens (1-2)
the specimens(3-4)Voltage
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the specimens(5-6)
voltageCurrent time
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voltageCurrent time
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voltageCurrent time
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voltageCurrent time
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voltageCurrent time
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