anticorrosion performance of ldh coating prepared by

Research ArticleAnticorrosion Performance of LDH Coating Prepared byCO2 Pressurization Method

Xiaochen Zhang 12 Peng Jiang 3 Chunyan Zhang4 Bateer Buhe2 Bin Liu1 Yang Zhao1

Tao Zhang 45 Guozhe Meng1 and FuhuiWang5

1College of Materials Science and Chemical Engineering Harbin Engineering University Harbin 150001 China2College of Materials Chemical and Engineering Heilongjiang Institute of Technology Harbin 150050 China3School of Mechanical Engineering Changzhou University Changzhou 213164 China4Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China5School of Materials Science and Engineering Northeastern University Shenyang 110819 China

Correspondence should be addressed to Tao Zhang zhangtaomailneueducn

Received 22 May 2018 Revised 21 August 2018 Accepted 10 September 2018 Published 27 September 2018

Academic Editor Ramazan Solmaz

Copyright copy 2018 XiaochenZhang et alThis is an open access article distributed under theCreativeCommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Many surface treatment methods are used to improve the corrosion resistance of magnesium alloys LDH (layered doublehydroxides) conversion coatings are currently found in the most environmentally friendly and pollution-free coatings ofmagnesium alloy In this study the CO2 pressurization method was applied to the preparation of LDH coating on magnesiumalloy for the first timeThe effect of CO2 pressurization on the formation and corrosion resistance of LDH coating on AZ91D alloywas investigated The hardness and adhesion were significantly higher on LDH coating in the case of CO2 pressurization than itis in atmospheric pressure The surface and cross-sectional morphologies show that LDH coating is more compact in the case ofCO2 pressurization than with atmospheric pressureThe results of the polarization curve hydrogen evolution and immersion testsindicate that the corrosion resistance of the LDH coating prepared by the CO2 pressurization method was significantly improved

1 Introduction

Magnesium and magnesium alloys are a ldquogreen engineeringmaterialrdquo in the 21st century having a wide range of appli-cation prospects such as automotive in aerospace portableelectronic devices and in medicine This is due to theirsuperior strength-weight ratio dimensional stability lightweight recycling ability and other excellent properties [12] However the corrosion resistance of magnesium andmagnesium alloys is extremely poor severely restricting theirfurther development [3 4] In order to expand the applicationof magnesium alloy and improve its corrosion resistance thecorrosion mechanism and surface protection of magnesiumalloy materials have been studied extensively by domesticand foreign scholars [5ndash9] Through surface modificationand the coating on the surface of magnesium alloy thedefects of the corrosion resistance of magnesium alloys canbe improved economically and effectively Examples of this

include conversion coating [10ndash12] anode oxidation [13 14]electroplating [15 16] and physical vapor deposition (PVD)[17 18] among which the most widely used in the pastdecade is chromate conversion coating Chromate conversioncoating is a simple process with the product coating demon-strating good heat stability and providing good protectionfor the magnesium alloy However chromate is toxic to theenvironment and hazardous to human beings leading to itbeing banned in recent years Lately focus has turned toconversion coating that contains no chromium [12 19 20]such as phosphate [21 22] phosphate-permanganate [23ndash25] stannate [26 27] vanadate [28 29] cerate [27 30]lanthanite [31] and LDHs surface coatings [32ndash36] Of theseLDH surface coating as an environmentally friendly coatinghas attracted more attention as it brings no pollution to theenvironment

Layered double hydroxides (LDH) are environmentallyfriendly intercalation compounds They are represented by

HindawiInternational Journal of CorrosionVolume 2018 Article ID 9696549 10 pageshttpsdoiorg10115520189696549

2 International Journal of Corrosion

Table 1 Preparation parameters for three kinds of LDH conversion coatings

Parameters Temperature ∘C pH Time h Pressure MPa1 [39 40] CO2 24h 50 43 24 012 [41ndash43] CO2 2hpH115 2h 50 43115 4 013 CO2 3MPa 05h 50 43 05 3

In the 3MPa 50∘C water soluble Ultrasonic cleaning wasperformed in anhydrousethanol for 10min

AZ91D magnesiumAlloy specimen

A 2mm round hole in the middle positionof the sample is used for suspensionsample

carbonate let stand for 30 min

Obtain hydrotalcite conversion coating

Grind the sand paper with1000-2000 water

Figure 1 Operations for the preparation of conversion coating with CO2 pressurization method

a general formula of [M1minusx2+Mx3+(OH)2][A

nminus]xnsdotmH2Owhere M2+ and M3+ represent divalent (eg Mg2+ Ca2+Cu2+ Mn2+ Ni2+ and Zn2+) and trivalent metallic cations(eg Al3+ Cr3+ Fe3+ Mn3+ and Co3+) respectively Xindicates the molar ratio of M3+(M2++ M3+) and its valueranges from 020 to 033 finally with Anminus being an nminus valentanion which is exchangeable anions The anions (eg ClminusCO32minus NO3

minus and SO42minus) and variety of organic anions

can be exchanged between the outside and interlayer spacesoccupied by the water molecules [37 38] Uan et al [39ndash43]proposed the characterization of Mg-Al hydrotalcite conver-sion coating on Mg alloy Chen et al [44ndash46] studied thein situ growth mechanism of Mg-Al hydrotalcite conversioncoating on AZ31 magnesium alloy Syu et al [47] furtherstudied an Li-Al-CO3 double-phase hydroxide coating LaterZhang et al [48] used a coprecipitation method to synthe-size layered double hydroxides containing magnesium alloyWang et al [49] synthesized hydrotalcite conversion coatingon magnesium alloy

In this study considering the time consuming and weakantipollution properties owing to the complex process prepa-ration of LDH conversion coatings for former process anewmethod CO2 pressurizationmethod for preparing LDHconversion coatings was proposedThe introduction of a CO2pressurization method is based on the previous studies ofUan et al [39ndash43] LDH conversion coatings are preparedefficiently and quickly under CO2 pressurization A system-atic investigation of the microstructure hardness adhesionand corrosion resistance of LDHconversion coating is carriedout

2 Experiment

21 Material For the purposes of this paper AZ91D magne-sium alloy was selected as the object material to be studied

It is composed of 88 wt Al 069 wt Zn 0212 wtMn 002 wt Si 0002 wt Cu 0005 wt Fe and 0001wt Ni The AZ91D magnesium alloy ingot was cut into20mmtimes12mmtimes6mm samples each of which was groundwith 1000-2000-mesh SiC abrasive paper and ultrasonicallycleaned in anhydrous ethanol

22 Conversion Bath and Preparation of LDH Coating All ofthe reagentsreactants used were clean and nonpolluting Ina typical preparation the CO2 was introduced in deionizedwater at room temperature with the flow rate of 1 dm3minfor 20 min in order to form the CO3

2minusHCO3minus solution The

pH of the bath was approximately 43 [39] The LDH coatingwas prepared by means of three methods (see Table 1)

The first LDH coating was prepared by a one-step immer-sion method The specimens were statically immersed in thebath at 50∘C for a particular period for 24h denoted aboveas CO2 24h treatment [39 40]The second LDH coating wasprepared by a two-step immersion method The specimenswere immersed in the bath and CO2 gas was continuouslybubbled for 2h Subsequently the prep-treating bath wasmaintained at pH 115 by the dropwise addition of 125 Maqueous NaOH with vigorous stirring The prep-treatingspecimens were immediately hydrothermally treated suchtreating at 50∘C for 2hThe two-step treatmentwas denoted asCO2 2 hpH115 2h [41ndash43] The third LDH coating was pre-pared by the CO2 pressurization method (see Figure 1) Thebath was placed in an autoclave and then pressurized to 3MPaby pumping CO2 gas with the specimens of magnesium alloybeing immersed in the autoclave at 50∘C and under for 05hThis was denoted above as CO2 3MPa 05h

23 Hardness and Adhesion TheHVS-5 digital Vickers hard-ness was used to test the Vickers hardness with 5Kgf beingloaded for 10s The QFH type paint film was used to test the

International Journal of Corrosion 3

Table 2 Adhesion test results of LDH conversion coatings with various processes

Adhesions Adhesion klass Affected rate1 CO2 24h 1 lt52CO2 2hpH115 2h 1 lt53 CO2 3MPa 05h 0 Almost never off

adhesion of the LDH coating with the test results of the LDHcoating being observed according to ISO2409-1974

24 Microstructure The surface and cross-sectional mor-phologies of LDH coating were observed by a Philips XL30and JEOL JSM-6700F SEM respectively The microstruc-ture was analyzed with X-ray diffraction (GAXRD) at Cuk1205721(15405 A)

25 Corrosion Resistance Potentiodynamic polarizationmeasurements of AZ91D alloy with and without LDHcoating were performed in an electrochemical workstation(Zennium Zahner) with a three-electrode cell using aplatinum foil as the counter electrode and a saturatedcalomel electrode (SCE saturated KCl) as the referenceelectrode in aerated 35wt NaCl solution The corrosion ofmagnesium alloy is mainly shown as the hydrogen evolutionof the cathode In order to avoid the influence of the cathodeprocess on the whole electrochemical testing process theanodic and cathodic polarization curves of the specimenswere measured from the open circuit potential (OCP) to theanodic and cathodic side in the 300mv range with a scanrate of 0333mVsdotsminus1 respectively The above measurementswere repeated at least five times Hydrogen evolution datawere measured by collecting hydrogen from the reactionin a hydrogen collector The samples were placed in abeaker containing 35wt NaCl solution and in a waterbath pot with a constant temperature (30plusmn1∘C) The burettewas connected to the funnel inverted into the solutionperpendicular to the sample to be tested with it being notedthat the top of the burette should be fully immersed in thesolution The hydrogen bubble produced by the magnesiumalloy corrosion was introduced into the burette through thefunnel so that the hydrogen evolution rate of the magnesiumalloy and the film could be determined by the change of thereading on the burette after the hydrogen is collected Allof the hydrogen measurements were repeated at least threetimes The immersion test was conducted to determine thecorrosion rate of the AZ91D alloy with different LDH coatingfor 120 hours with the macroscopic corrosion morphologiesbeing obtained using a digital camera For the immersiontest all measurements were repeated at least three times at30 plusmn 1∘C

3 Results and Discussion

31 Effect of CO2 Pressurization on Hardness and AdhesionThe effect of the CO2 pressurization method on the hardnessof the magnesium alloy surface is shown in Figure 2

1 2 3 4 5 6

100

150

200

250

300

350

HV

ab

cd

a

b

cd

Points

AZ91DCO2_24h

CO2_2hpH115_2hCO2_3MPa_05h

Figure 2 Hardness test results of the AZ91D alloy with and withoutLDH conversion coating

The surface hardness was improved by the surfacetreatment and the hardness increased even more of theCO2 3MPa 05h LDH coating The macroscopic morpholo-gies of the three specimens with different surface treatmentsafter adhesion test are shown in Figure 3 where it can beclearly seen that the LDH coating detachment from thesurface of the specimens was a mixed adhesivecohesivefracture

The results of the adhesion test are shown in Table 2)The cross cut tests are used to evaluate the adhesion of theconversion coating by attaching a 3M tape to the surface of thesample cross cut and removing it so as to observe the degreeof detachment of the coating layer from the substrate For theCO2 2hpH115 2h andCO2 24h coating samples the peelingarea of the conversion film was less than 5 The coatingsample of CO2 3MPa 05h showed almost never anything offof it This suggests that the adhesion values can be ranked inthe following descending order CO2 3MPa 05h gt CO2 24hasymp CO2 2hpH115 2h

32 Effect of CO2 Pressurization on Microstructure The sur-face and cross-sectional morphologies of LDH coating areshown in Figures 4 and 5 The surface morphology of theCO2 3MPa 05h LDH coating was completely different fromthose of CO2 24h and CO2 2hpH115 2h The microcrackson the coating surface of CO2 3MPa 05h almost disap-peared resulting in a dense and flat surface with island-like


500m

(a)

500m

(b)

500m

(c)

Figure 3 Adhesion test of conversion coatings with various process on AZ91D alloys (a) CO2 24h (b) CO2 2hpH115 2h and (c)CO2 3MPa 05h

20m20m

20m20m

(a) (b)

(c) (d)

Figure 4 Morphologies of conversion coatings with various processes on AZ91D alloys (a) unhandled-AZ91D (b) CO2 24h (c)CO2 2hpH115 2h and (d) CO2 3MPa 05h

features Moreover the cross-sectional morphology obser-vation indicates that the CO2 3MPa 05h LDH coating iscompact integral and with less microcracks

Opposed to this CO2 24h and CO2 2hpH115 2h showa large number of microcracks on the LDH coating with thepossibility that there are some cracks reaching the interfacebetween the coating and the substrate

The XRD patterns of the cast and different conversioncoatings of AZ91D alloy are shown inFigure 6Thediffractionpeaks of 120572-Mg Mg17Al12 and LDH were detected Therewere no discrepancies in the crystallographic orientationswith the diffraction peaks of LDH between the CO2 24hCO2 2hpH115 2h and CO2 3Mpa 05h specimens How-ever there were higher peaks of LDH on the CO2 3Mpa 05h

specimen indicating that the CO2 pressurization method iseasier for promoting the dynamic crystallization process ofLDH conversion film on AZ91D magnesium alloy surfaces

33 Effect of CO2 Pressurization on Corrosion Resistance Thepotentiodynamic polarization curves of the AZ91D alloy withand without conversion coatings are shown in Figure 7

The corresponding electrochemical parameters includ-ing corrosion potential (Ecorr) corrosion current density(119894corr) and percentage of efficiencies (efficiency) are calcu-lated from the curves and listed in Table 3

The hydrogen evolution rate (HER) of the AZ91D alloywith and without conversion coating is shown in Figure 8


10m

AZ91D

(a)

10m

CO2_24h

(b)

10m

CO2_2hpH115_2h

(c)

10m

CO2_3MPa_05h

(d)

Figure 5 Cross-sectional microstructures of conversion coatings with various processes on AZ91D alloys (a) unhandled-AZ91D (b)CO2 24h (c) CO2 2hpH115 2h and (d) CO2 3MPa 05h

10 20 30 40 50

Inte

nsity

(au

)

2 (deg)

LDHsMgMg17Al12

CCO2_24h

BCO2_2h_2h

ACO2_3MPa_05h

DAZ91D

Figure 6 GAXRD patterns of the AZ91D alloy with and withoutconversion coating

It is well-known that the HER is proportional to the cor-rosion rate [48ndash52] After the conversion treatment theHER of CO2 3MPa 05h coated AZ91D alloy (0624plusmn0028mLsdothminus1sdotcmminus2) is lower by nearly 3 times that of the bare

1E-7 1E-6 1E-5 1E-4 1E-3minus155

minus150

minus145

minus140

minus135

minus130

minus125

E SHE

(V)

ab

cd

ab

cd

AZ91DCO2_24h


i (A∙ cm2)

Figure 7 Polarization curves of the AZ91D alloy with and withoutconversion coating conversion coatings tested in 35wt NaClsolution

AZ91D alloy (1920plusmn0114 mLsdothminus1sdotcmminus2) implying that con-version coating improves the corrosion resistance of AZ91Dalloy Moreover the HER of CO2 3MPa 05h coating wasapproximately equal to that of the CO2 2hpH115 2h coatingand lower than that of the CO2 24h coating An immersion


0 10 20 30 40 50

00

05

10

15

20

hydr

ogen

evol

utio

n (m

lcm

2 )

Time (h)

a

b

c

d

ab

cd

AZ91DCO2_24h


Figure 8 Hydrogen Evolution Curve of the AZ91D alloy with andwithout conversion coating in 06M NaCl solution

test of 120 hwas employed to evaluate the corrosion resistanceof the conversion coatings Themacroscopic morphologies ofAZ91D alloy with and without conversion coating are shownin Figure 9

According to the Butler-Volmer equation the corrosioncurrent density (119894corr) should be determined based on thecathodic branch of the polarization curves by theTafel extrap-olation method [50] with 119894corr being equal to the intersectionof the horizontal line of the corrosion potential (Ecorr) andthe Tafel line of the cathodic process It can be seen thatthe anodic reaction of AZ91D alloy is significantly inhibitedEcorr of the CO2 3MPa 05h coating (-136 V) is higher thanthat of the AZ91D alloy (-141 V) Furthermore 119894corr of thecoated AZ91D alloy (892plusmn137 120583Acmminus2) is lower by nearlyone order of magnitude than that of the bare AZ91D alloy(8362plusmn163 120583Acmminus2) indicating that the conversion coatingeffectively enhanced the corrosion resistance of the AZ91Dalloy Compared to the CO2 24h and CO2 2hpH115 2hLDH coatings the corrosion resistance of CO2 3MPa 05h isalso higher than the CO2 24h and CO2 2hpH115 2h LDHcoatings embodying the lower 119894corr Moreover the percentageof efficiencies (efficiency) which is calculated from theratio of 119894corr with and without conversion coating also showsthat CO2 3MPa 05h gt CO2 2hpH115 2h gt CO2 24h Theabove results show that 119894corr of LDH coating can be ranked inthe increasing series CO2 3MPa 05hltCO2 2hpH115 2h ltCO2 24h

Additionally the percentage of the surface area rustedfor each specimen is estimated by using the visual exam-ples according to ASTM D610-08 It is evident that thebare AZ91D alloy underwent severe attack rust grade 3GMeanwhile only several corroded spots are observed onthe surfaces of the CO2 3MPa 05h CO2 2hpH115 2h andCO2 24h coated specimens where the corresponding rustgrades were 7G 7G and 6G respectively The results of theimmersion test are in good agreement with those of the

polarization curve and HER indicating the improvement ofthe corrosion resistance of AZ91D alloy after CO2 3MPa 05hconversion treatment

According to the above results the anticorrosionperformance of LDH coating can be ranked in the followingdecreasing series CO2 3MPa 05h asymp CO2 2hpH115 2hgt CO2 24h However the preparation efficiency ofCO2 3MPa 05h coating is 8 and 48 times higher than that ofthe CO2 2hpH115 2h and CO2 24h coatings Consideringthe corrosion resistance and preparation efficiency of thethree coatings the performance of CO2 3MPa 05h coatingis superior to that of the CO2 2hpH115 2h and CO2 24hcoatings

34 Effect of CO2 Pressurization on Film-Forming PowerProcess The film-forming process of the LDH conversioncoating is a kind of physical and chemical processes Thereaction process of the AZ91D magnesium alloy matrixmaterial mainly includes an electrochemical reaction an ion-ization reaction and a coating-forming reaction in carbonatesolution Its specific chemical reaction equation is shown informulae (1)sim(6) [50ndash52]

119872119892 minus 2119890minus 997888rarr 1198721198922+ (1)

119860119897 minus 3119890minus 997888rarr 1198601198973+ (2)

2119867+ + 2119890minus 997888rarr 1198672 (119892) (3)

11986721198621198743 997888rarr 119867119862119874minus

3 + 119867+ (4)

11986721198621198743 997888rarr 1198621198742minus

3 + 2119867+ (5)

61198721198922+ + 21198601198973+ + 1198621198742minus3 + 16119874119867minus + 41198672119874 997888rarr

11987211989261198601198972 (119874119867)16 1198621198743 sdot 41198672119874(6)

The electrochemical reactions are shown in (1) (2) and(3) with it mainly being characterized as the dissolution ofthe metal of the anode and hydrogen ions of the cathodeoverflow The ionization reactions are shown in (4) and (5)it basically being the ionization of the carbonate solutioninto the process of carbonate ions and bicarbonate ionsThe film-forming reaction is shown in (6) with it mainlybeing the formation of a hydrotalcite conversion coatingprocess with magnesium ions aluminium ions carbonateions hydroxyl ions and an aqueous solution The vaporpressure of the solute in the dilute solution is proportional tothe concentration of the solution according to Henryrsquos lawThe higher the temperature the smaller the solubility thegreater the pressure and the greater the solubility at a certaintemperature

Due to the CO2 pressurization the CO2 solubility in thesolution increased with the proportion of carbonate ionsin the solution also increasing resulting in an increase inthe hydrogen ion concentration increased and promoting theelectrochemical reaction to the right thus accelerating thedissolution of the aluminium and magnesium ions Furtherdue to the CO2 pressurization the ionization is promoted toa positive reaction accelerating increasing the hydroxyl ions


10mm

a1 b1 c1 d1

a2 b2 c2 d2

a3 b3 c3 d3

a4 b4 c4 d4

a5 b5 c5 d5

Figure 9 Optical corrosion morphologies of the AZ91D alloy with and without conversion coating of immersing test in 06M NaCl (a1)nonimmersed original sample (a2) original sample immersed for 24h (a3) original sample immersed for 48h (a4) original sample immersedfor 72h (a5) original sample immersed for 120h (b1) nonimmersed CO2 24h sample (b2) CO2 24h sample immersed for 24h (b3) CO2 24hsample immersed for 48h (b4) CO2 24h sample immersed for 72h (b5) CO2 24h sample immersed for 120h (c1) nonimmersed CO2 2hpH115 2h sample (c2) CO2 2hpH115 2h sample immersed for 24h (c3) CO2 2h pH115 2h sample immersed for 48h (c4) CO2 2hpH115 2h sample immersed for 72h (c5) CO2 2h pH115 2h sample immersed for 120h (d1) nonimmersed CO2 3MPa 05h sample (d2)CO2 3MPa 05h sample immersed for 24h (d3) CO2 3MPa 05h sample immersed for 48h (d4) CO2 3MPa 05h sample immersed for 72hand (d5) CO2 3MPa 05h sample immersed for120h

Table 3 Electrochemical test results of the AZ91D alloy with and without LDH conversion coating

Samples AZ91D CO2 2hpH115 2h CO2 24h CO2 3Mpa 05hEcorr (V SCE) 141(plusmn0059) -136(plusmn0026) 134(plusmn0054) -136(plusmn0034)119894corr (120583Acm

2) 8362(plusmn167) 1581(plusmn169) 1734(plusmn178) 892(plusmn163)efficiency - 811 793 893

in the solution and at the same time increasing the ionizationreaction to the right with the concentration of carbonateion and bicarbonate ion in the solution being increased Theacceleration of the electrochemical reaction and ionizationpromoted the film-forming of the magnesium alloy matrixand the increase of the magnesium ions aluminium ioncarbonate ions and hydroxyl ions promoting the film to apositive reaction and eventually improving the film-formingreaction rateThe film-forming process is shown in Figure 10

In the initial stages the conversion coating was very thinwith a small angular cavity or pit such as a honeycombcell as can be seen in Figure 10(a) With the extension ofthe coating formation time the conversion coating beganto thicken and grow with layer as shown in Figure 10(b)The surface was completely covered at 30 min as show inFigure 10(c) With the cross-section of the coating it can befound that the conversion coating first became in the 120572-Mgphase with the conversion coating also present in the120573-phase

as the processing time increased At 30 min the surface ofthe magnesium alloy was covered with a complete and densehydrotalcite conversion coating (see Figure 10)

4 Conclusion

The CO2 pressurization method was first applied to thepreparation of LDH coating on AZ91D alloy The conversioncoating first became in the 120572-Mg phase with the conversioncoating also present in the 120573-phase as the processing timeincreased The formation rate of LDH coating was increasedindicating that the preparation efficiency can be improvedgreatly under CO2 pressurization Through this method anLDH coating with higher thickness and less microcracksformed on the AZ91D alloy significantly enhancing its anti-corrosion performance Compared to traditional processedthe anticorrosion performance of the CO2 3MPa 05h coat-ing was approximately equal to that of the CO2 2hpH115 2h


20m

(a)

20m

(b)

20m

(c)

LDH

-phase

eutectic phase

-phase

Time 10min

Time 20min

Time 30min

2m

(d)

Figure 10 The film-forming process of the LDH conversion coating on the AZ91D magnesium alloy matrix material (a) morphologiesof the 10min sample (b) morphologies of the 20min sample (c) morphologies of the 30min sample and (d) cross-sectional of conversioncoating-forming process

coating and was higher than that of the CO2 24h coatingConsidering the anticorrosion performance and preparationefficiency the CO2 pressurization method is a promisinggreen technique for preparing LDH coating on magnesiumalloy

Data Availability

You can access the data through the link httpsfairsharingorgaccountsprofile

Conflicts of Interest

The authors hereby declare that there are no conflicts ofinterest regarding the publication of this paper

Acknowledgments

The authors wish to acknowledge the financial support of theNational program for the Young Top-notch Professionals theNational Natural Science Foundation of China (nos 5153100751771050 and 51705038) and Foundation of Young Scholarsin HLJIT (2014QJ12)

References

[1] A Atrens G-L SongM Liu Z Shi F Cao andM SDarguschldquoReview of recent developments in the field of magnesium

corrosionrdquo Advanced Engineering Materials vol 17 no 4 pp400ndash453 2015

[2] Y Zhao L Shi X Ji et al ldquoCorrosion resistance and antibac-terial properties of polysiloxane modified layer-by-layer assem-bled self-healing coating onmagnesiumalloyrdquo Journal ofColloidand Interface Science vol 526 pp 43ndash50 2018

[3] F Cao G-L Song and A Atrens ldquoCorrosion and passivationof magnesium alloysrdquo Corrosion Science vol 111 pp 835ndash8452016

[4] M Esmaily JE Svensson et al ldquoFundamentals and advances inmagnesiumalloy corrosionrdquoProgMater Sci vol 89 pp 92ndash1932017

[5] M Strzelecka J IwaszkoMMalik and S Tomczynski ldquoSurfacemodification of the AZ91 magnesium alloyrdquo Archives of Civiland Mechanical Engineering vol 15 no 4 pp 854ndash861 2015

[6] Y Su YGuo ZHuang et al ldquoPreparation and corrosion behav-iors of calcium phosphate conversion coating on magnesiumalloyrdquo Surface and Coatings Technology vol 307 pp 99ndash1082016

[7] Y Gao L Zhao X Yao R Hang X Zhang and B TangldquoCorrosion behavior of porousZrO 2 ceramic coating onAZ31Bmagnesiumalloyrdquo Surface andCoatings Technology vol 349 pp434ndash441 2018

[8] J Yuan R Yuan J Wang et al ldquoFabrication and corrosionresistance of phosphateZnO multilayer protective coating onmagnesiumalloyrdquo Surface and Coatings Technology vol 352 pp74ndash83 2018

[9] X Wang L Li Z Xie and G Yu ldquoDuplex coating combininglayered double hydroxide and 8-quinolinol layers on Mg alloy


for corrosion protectionrdquo Electrochimica Acta vol 283 pp1845ndash1857 2018

[10] Z Shao Z Cai and J Shi ldquoPreparation and Performance ofElectroless Nickel on AZ91D Magnesium AlloyrdquoMaterials andManufacturing Processes vol 31 no 9 pp 1238ndash1245 2016

[11] M Esmaily D B Blucher J E Svensson M Halvarsson and LG Johansson ldquoNew insights into the corrosion of magnesiumalloysmdashthe role of aluminumrdquo Scripta Materialia vol 115 pp91ndash95 2016

[12] R Zeng Y Hu F Zhang et al ldquoCorrosion resistance of cerium-doped zinc calcium phosphate chemical conversion coatingson AZ31 magnesium alloyrdquo Transactions of Nonferrous MetalsSociety of China vol 26 no 2 pp 472ndash483 2016

[13] G-L Song and Z Shi ldquoCorrosion mechanism and evaluationof anodized magnesium alloysrdquo Corrosion Science vol 85 pp126ndash140 2014

[14] A F Cipriano J Lin C Miller et al ldquoAnodization of mag-nesium for biomedical applications ndash Processing characteri-zation degradation and cytocompatibilityrdquo Acta Biomaterialiavol 62 pp 397ndash417 2017

[15] I Saeki T Seguchi Y Kourakata and Y Hayashi ldquoNi elec-troplating on AZ91D Mg alloy using alkaline citric acid bathrdquoElectrochimica Acta vol 114 pp 827ndash831 2013

[16] D Yan G Yu B Hu J Zhang Z Song and X Zhang ldquoAninnovative procedure of electroless nickel plating in fluoride-free bath used for AZ91D magnesium alloyrdquo Journal of Alloysand Compounds vol 653 pp 271ndash278 2015

[17] H Altun and S Sen ldquoThe effect of PVD coatings on the wearbehaviour of magnesium alloysrdquo Materials Characterizationvol 58 no 10 pp 917ndash921 2007

[18] H Hoche S Groszlig and M Oechsner ldquoDevelopment of newPVD coatings for magnesium alloys with improved corrosionpropertiesrdquo Surface and Coatings Technology vol 259 pp 102ndash108 2014

[19] S Pommiers J Frayret A Castetbon and M Potin-GautierldquoAlternative conversion coatings to chromate for the protectionof magnesium alloysrdquo Corrosion Science vol 84 pp 135ndash1462014

[20] X Jiang R Guo and S Jiang ldquoMicrostructure and corrosionresistance of Ce-V conversion coating on AZ31 magnesiumalloyrdquo Applied Surface Science vol 341 pp 166ndash174 2015

[21] X-B Chen H-Y Yang T B Abbott M A Easton and NBirbilis ldquoCorrosion protection of magnesium and its alloys bymetal phosphate conversion coatingsrdquo Surface Engineering vol30 no 12 pp 871ndash879 2014

[22] N Van Phuong M Gupta and S Moon ldquoEnhanced corrosionperformance of magnesium phosphate conversion coating onAZ31 magnesium alloyrdquo Transactions of Nonferrous MetalsSociety of China vol 27 no 5 pp 1087ndash1095 2017

[23] S-Y Jian Y-R Chu and C-S Lin ldquoPermanganate conversioncoating on AZ31 magnesium alloys with enhanced corrosionresistancerdquo Corrosion Science vol 93 pp 301ndash309 2015

[24] Y L Lee Y R Chu W C Li and C S Lin ldquoEffect ofpermanganate concentration on the formation and propertiesof phosphatepermanganate conversion coating on AZ31 mag-nesium alloyrdquo Corrosion Science vol 70 pp 74ndash81 2013

[25] M Mosiałek G Mordarski P Nowak et al ldquoPhosphate-permanganate conversion coatings on the AZ81 magnesiumalloy SEM EIS and XPS studiesrdquo Surface and Coatings Tech-nology vol 206 no 1 pp 51ndash62 2011

[26] L Yang M Zhang J Li X Yu and Z Niu ldquoStannate conversioncoatings onMg-8Li alloyrdquo Journal of Alloys andCompounds vol471 no 1-2 pp 197ndash200 2009

[27] Y L Lee Y R Chu F J Chen and C S Lin ldquoMechanism ofthe formation of stannate and cerium conversion coatings onAZ91Dmagnesium alloysrdquoApplied Surface Science vol 276 pp578ndash585 2013

[28] Y Ma N Li D Li M Zhang and X Huang ldquoCharacteristicsand corrosion studies of vanadate conversion coating formedon Mg-14 wtLi-1 wtAl-01 wtCe alloyrdquo Applied SurfaceScience vol 261 pp 59ndash67 2012

[29] L Niu S-H Chang X Tong G Li and Z Shi ldquoAnalysis ofcharacteristics of vanadate conversion coating on the surface ofmagnesiumalloyrdquo Journal of Alloys andCompounds vol 617 pp214ndash218 2014

[30] L Lei J Shi X Wang D Liu and H Xu ldquoMicrostructureand electrochemical behavior of cerium conversion coatingmodified with silane agent on magnesium substratesrdquo AppliedSurface Science vol 376 pp 161ndash171 2016

[31] G Kong L Liu J Lu C Che and Z ZHong ldquoStudy onlanthanum salt conversion coating modified with citric acid onhot dip galvanized steelrdquo Journal of Rare Earths vol 28 no 3pp 461ndash465 2010

[32] N Kamiyama G Panomsuwan E Yamamoto T SudareN Saito and T Ishizaki ldquoEffect of treatment time in theMg(OH)2MgndashAl LDH composite film formed on Mg alloyAZ31 by steam coating on the corrosion resistancerdquo Surface andCoatings Technology vol 286 pp 172ndash177 2016

[33] Q Dong Z Ba and Y Jia ldquoEfect of solution concentrationon sealing treatment of Mg-Al hydrotalcite film on AZ91D Mgalloyrdquo J Magnes Alloy vol 5 pp 320ndash325 2017

[34] L Guo W Wu Y Zhou F Zhang R Zeng and J ZengldquoLayered double hydroxide coatings on magnesium alloys Areviewrdquo Journal of Materials Science and Technology vol 34 no9 pp 1455ndash1466 2018

[35] G Zhang L Wu A Tang et al ldquoGrowth behavior of MgAl-layered double hydroxide films by conversion of anodic films onmagnesium alloy AZ31 and their corrosion protectionrdquo AppliedSurface Science vol 456 pp 419ndash429 2018

[36] GZhang LWuATang et al ldquoSealing of anodizedmagnesiumalloy AZ31 with MgAl layered double hydroxides layersrdquo RSCAdvances vol 8 no 5 pp 2248ndash2259 2018

[37] H Hirahara S Aisawa T Akiyama et al ldquoIntercalation ofpolyhydric alcohols into MgndashAl layered double hydroxide bycalcination-rehydration reactionrdquo Clay Sci vol 13 pp 27ndash342005

[38] J-Y Uan J-K Lin and Y-S Tung ldquoDirect growth of orientedMg-Al layered double hydroxide film on Mg alloy in aqueousHCOminus

3 CO2minus

3 solutionrdquo Journal of Materials Chemistry vol 20no 4 pp 761ndash766 2010

[39] J K Lin C L Hsia and J Y Uan ldquoCharacterization of MgAl-hydrotalcite conversion film on Mg alloy and Cl- and CO32 -anion-exchangeability of the film in a corrosive environmentrdquoScripta Materialia vol 56 no 11 pp 927ndash930 2007

[40] J-YUan J-K Lin Y-S SunW-E Yang L-K Chen andH-HHuang ldquoSurface coatings for improving the corrosion resistanceand cell adhesion of AZ91Dmagnesium alloy through environ-mentally clean methodsrdquo Thin Solid Films vol 518 no 24 pp7563ndash7567 2010

[41] J K Lin and J Y Uan ldquoFormation of MgAl-hydrotalciteconversion coating on Mg alloy in aqueous HCO3-CO32- and


corresponding protection against corrosion by the coatingrdquoCorrosion Science vol 51 no 5 pp 1181ndash1188 2009

[42] B Yu J Lin and J Uan ldquoApplications of carbonic acid solutionfor developing conversion coatings onMg alloyrdquoTransactions ofNonferrous Metals Society of China vol 20 no 7 pp 1331ndash13392010

[43] J-K Lin K-L Jeng and J-YUan ldquoCrystallization of a chemicalconversion layer that forms on AZ91D magnesium alloy incarbonic acidrdquo Corrosion Science vol 53 no 11 pp 3832ndash38392011

[44] J Chen Y Song D Shan and E-H Han ldquoIn situ growth ofMg-Al hydrotalcite conversion film on AZ31 magnesium alloyrdquoCorrosion Science vol 53 no 10 pp 3281ndash3288 2011

[45] J Chen Y Song D Shan and E-H Han ldquoStudy of the in situgrowth mechanism of Mg-Al hydrotalcite conversion film onAZ31 magnesium alloyrdquo Corrosion Science vol 63 pp 148ndash1582012

[46] J ChenY SongD Shan andE-HHan ldquoStudyof the corrosionmechanismof the in situ grownMg-Al-CO32- hydrotalcite filmon AZ31 alloyrdquo Corrosion Science vol 65 pp 268ndash277 2012

[47] J-H Syu J-Y Uan M-C Lin and Z-Y Lin ldquoOpticallytransparent Li-Al-CO3 layered double hydroxide thin films onan AZ31 Mg alloy formed by electrochemical deposition andtheir corrosion resistance in a dilute chloride environmentrdquoCorrosion Science vol 68 pp 238ndash248 2013

[48] F Zhang Z-G Liu R-C Zeng et al ldquoCorrosion resistance ofMg-Al-LDH coating on magnesium alloy AZ31rdquo Surface andCoatings Technology vol 258 pp 1152ndash1158 2014

[49] L Wang K Zhang H He W Sun Q Zong and G LiuldquoEnhanced corrosion resistance of MgAl hydrotalcite conver-sion coating on aluminum by chemical conversion treatmentrdquoSurface and Coatings Technology vol 235 pp 484ndash488 2013

[50] G L Song ldquoCorrosion behavior of magnesium alloys andprotection techniquesrdquo Surf Eng Light Alloys pp 3ndash39 2010

[51] S Thomas N V Medhekar G S Frankel and N Birbilis ldquoCor-rosion mechanism and hydrogen evolution on Mgrdquo CurrentOpinion in Solid State ampMaterials Science vol 19 no 2 pp 85ndash94 2015

[52] D Song A B Ma J H Jiang P H Lin D H Yang and J FFan ldquoCorrosion behaviour of bulk ultra-fine grained AZ91Dmagnesiumalloy fabricated by equal-channel angular pressingrdquoCorrosion Science vol 53 no 1 pp 362ndash373 2011

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018


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Chemistry

Analytical ChemistryInternational Journal of


ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of



Advances in Condensed Matter Physics


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Journal ofEngineeringVolume 2018

Applied ChemistryJournal of


NanotechnologyHindawiwwwhindawicom Volume 2018

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High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in



ChemistryAdvances in


Advances inPhysical Chemistry


BioMed Research InternationalMaterials

Journal of


Na

nom

ate

ria

ls


Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom


Table 1 Preparation parameters for three kinds of LDH conversion coatings

Parameters Temperature ∘C pH Time h Pressure MPa1 [39 40] CO2 24h 50 43 24 012 [41ndash43] CO2 2hpH115 2h 50 43115 4 013 CO2 3MPa 05h 50 43 05 3

In the 3MPa 50∘C water soluble Ultrasonic cleaning wasperformed in anhydrousethanol for 10min

AZ91D magnesiumAlloy specimen

A 2mm round hole in the middle positionof the sample is used for suspensionsample

carbonate let stand for 30 min

Obtain hydrotalcite conversion coating

Grind the sand paper with1000-2000 water

Figure 1 Operations for the preparation of conversion coating with CO2 pressurization method

a general formula of [M1minusx2+Mx3+(OH)2][A

nminus]xnsdotmH2Owhere M2+ and M3+ represent divalent (eg Mg2+ Ca2+Cu2+ Mn2+ Ni2+ and Zn2+) and trivalent metallic cations(eg Al3+ Cr3+ Fe3+ Mn3+ and Co3+) respectively Xindicates the molar ratio of M3+(M2++ M3+) and its valueranges from 020 to 033 finally with Anminus being an nminus valentanion which is exchangeable anions The anions (eg ClminusCO32minus NO3

minus and SO42minus) and variety of organic anions

can be exchanged between the outside and interlayer spacesoccupied by the water molecules [37 38] Uan et al [39ndash43]proposed the characterization of Mg-Al hydrotalcite conver-sion coating on Mg alloy Chen et al [44ndash46] studied thein situ growth mechanism of Mg-Al hydrotalcite conversioncoating on AZ31 magnesium alloy Syu et al [47] furtherstudied an Li-Al-CO3 double-phase hydroxide coating LaterZhang et al [48] used a coprecipitation method to synthe-size layered double hydroxides containing magnesium alloyWang et al [49] synthesized hydrotalcite conversion coatingon magnesium alloy

In this study considering the time consuming and weakantipollution properties owing to the complex process prepa-ration of LDH conversion coatings for former process anewmethod CO2 pressurizationmethod for preparing LDHconversion coatings was proposedThe introduction of a CO2pressurization method is based on the previous studies ofUan et al [39ndash43] LDH conversion coatings are preparedefficiently and quickly under CO2 pressurization A system-atic investigation of the microstructure hardness adhesionand corrosion resistance of LDHconversion coating is carriedout

2 Experiment

21 Material For the purposes of this paper AZ91D magne-sium alloy was selected as the object material to be studied

It is composed of 88 wt Al 069 wt Zn 0212 wtMn 002 wt Si 0002 wt Cu 0005 wt Fe and 0001wt Ni The AZ91D magnesium alloy ingot was cut into20mmtimes12mmtimes6mm samples each of which was groundwith 1000-2000-mesh SiC abrasive paper and ultrasonicallycleaned in anhydrous ethanol

22 Conversion Bath and Preparation of LDH Coating All ofthe reagentsreactants used were clean and nonpolluting Ina typical preparation the CO2 was introduced in deionizedwater at room temperature with the flow rate of 1 dm3minfor 20 min in order to form the CO3

2minusHCO3minus solution The

pH of the bath was approximately 43 [39] The LDH coatingwas prepared by means of three methods (see Table 1)

The first LDH coating was prepared by a one-step immer-sion method The specimens were statically immersed in thebath at 50∘C for a particular period for 24h denoted aboveas CO2 24h treatment [39 40]The second LDH coating wasprepared by a two-step immersion method The specimenswere immersed in the bath and CO2 gas was continuouslybubbled for 2h Subsequently the prep-treating bath wasmaintained at pH 115 by the dropwise addition of 125 Maqueous NaOH with vigorous stirring The prep-treatingspecimens were immediately hydrothermally treated suchtreating at 50∘C for 2hThe two-step treatmentwas denoted asCO2 2 hpH115 2h [41ndash43] The third LDH coating was pre-pared by the CO2 pressurization method (see Figure 1) Thebath was placed in an autoclave and then pressurized to 3MPaby pumping CO2 gas with the specimens of magnesium alloybeing immersed in the autoclave at 50∘C and under for 05hThis was denoted above as CO2 3MPa 05h

23 Hardness and Adhesion TheHVS-5 digital Vickers hard-ness was used to test the Vickers hardness with 5Kgf beingloaded for 10s The QFH type paint film was used to test the









1 2 3 4 5 6

100

150

200

250

300

350

HV

ab

cd

a

b

cd

Points

AZ91DCO2_24h







500m

(a)

500m

(b)

500m

(c)


20m20m

20m20m

(a) (b)

(c) (d)










10m

AZ91D

(a)

10m

CO2_24h

(b)

10m

CO2_2hpH115_2h

(c)

10m

CO2_3MPa_05h

(d)


10 20 30 40 50

Inte

nsity

(au

)

2 (deg)

LDHsMgMg17Al12

CCO2_24h

BCO2_2h_2h

ACO2_3MPa_05h

DAZ91D



1E-7 1E-6 1E-5 1E-4 1E-3minus155

minus150

minus145

minus140

minus135

minus130

minus125

E SHE

(V)

ab

cd

ab

cd

AZ91DCO2_24h


i (A∙ cm2)




0 10 20 30 40 50

00

05

10

15

20

hydr

ogen

evol

utio

n (m

lcm

2 )

Time (h)

a

b

c

d

ab

cd

AZ91DCO2_24h









119872119892 minus 2119890minus 997888rarr 1198721198922+ (1)

119860119897 minus 3119890minus 997888rarr 1198601198973+ (2)

2119867+ + 2119890minus 997888rarr 1198672 (119892) (3)

11986721198621198743 997888rarr 119867119862119874minus

3 + 119867+ (4)

11986721198621198743 997888rarr 1198621198742minus

3 + 2119867+ (5)

61198721198922+ + 21198601198973+ + 1198621198742minus3 + 16119874119867minus + 41198672119874 997888rarr

11987211989261198601198972 (119874119867)16 1198621198743 sdot 41198672119874(6)




10mm

a1 b1 c1 d1

a2 b2 c2 d2

a3 b3 c3 d3

a4 b4 c4 d4

a5 b5 c5 d5








4 Conclusion



20m

(a)

20m

(b)

20m

(c)

LDH

-phase

eutectic phase

-phase

Time 10min

Time 20min

Time 30min

2m

(d)



Data Availability




Acknowledgments


References










































3 CO2minus




















Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls












1 2 3 4 5 6

100

150

200

250

300

350

HV

ab

cd

a

b

cd

Points

AZ91DCO2_24h







500m

(a)

500m

(b)

500m

(c)


20m20m

20m20m

(a) (b)

(c) (d)










10m

AZ91D

(a)

10m

CO2_24h

(b)

10m

CO2_2hpH115_2h

(c)

10m

CO2_3MPa_05h

(d)


10 20 30 40 50

Inte

nsity

(au

)

2 (deg)

LDHsMgMg17Al12

CCO2_24h

BCO2_2h_2h

ACO2_3MPa_05h

DAZ91D



1E-7 1E-6 1E-5 1E-4 1E-3minus155

minus150

minus145

minus140

minus135

minus130

minus125

E SHE

(V)

ab

cd

ab

cd

AZ91DCO2_24h


i (A∙ cm2)




0 10 20 30 40 50

00

05

10

15

20

hydr

ogen

evol

utio

n (m

lcm

2 )

Time (h)

a

b

c

d

ab

cd

AZ91DCO2_24h









119872119892 minus 2119890minus 997888rarr 1198721198922+ (1)

119860119897 minus 3119890minus 997888rarr 1198601198973+ (2)

2119867+ + 2119890minus 997888rarr 1198672 (119892) (3)

11986721198621198743 997888rarr 119867119862119874minus

3 + 119867+ (4)

11986721198621198743 997888rarr 1198621198742minus

3 + 2119867+ (5)

61198721198922+ + 21198601198973+ + 1198621198742minus3 + 16119874119867minus + 41198672119874 997888rarr

11987211989261198601198972 (119874119867)16 1198621198743 sdot 41198672119874(6)




10mm

a1 b1 c1 d1

a2 b2 c2 d2

a3 b3 c3 d3

a4 b4 c4 d4

a5 b5 c5 d5








4 Conclusion



20m

(a)

20m

(b)

20m

(c)

LDH

-phase

eutectic phase

-phase

Time 10min

Time 20min

Time 30min

2m

(d)



Data Availability




Acknowledgments


References










































3 CO2minus




















Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





500m

(a)

500m

(b)

500m

(c)


20m20m

20m20m

(a) (b)

(c) (d)










10m

AZ91D

(a)

10m

CO2_24h

(b)

10m

CO2_2hpH115_2h

(c)

10m

CO2_3MPa_05h

(d)


10 20 30 40 50

Inte

nsity

(au

)

2 (deg)

LDHsMgMg17Al12

CCO2_24h

BCO2_2h_2h

ACO2_3MPa_05h

DAZ91D



1E-7 1E-6 1E-5 1E-4 1E-3minus155

minus150

minus145

minus140

minus135

minus130

minus125

E SHE

(V)

ab

cd

ab

cd

AZ91DCO2_24h


i (A∙ cm2)




0 10 20 30 40 50

00

05

10

15

20

hydr

ogen

evol

utio

n (m

lcm

2 )

Time (h)

a

b

c

d

ab

cd

AZ91DCO2_24h









119872119892 minus 2119890minus 997888rarr 1198721198922+ (1)

119860119897 minus 3119890minus 997888rarr 1198601198973+ (2)

2119867+ + 2119890minus 997888rarr 1198672 (119892) (3)

11986721198621198743 997888rarr 119867119862119874minus

3 + 119867+ (4)

11986721198621198743 997888rarr 1198621198742minus

3 + 2119867+ (5)

61198721198922+ + 21198601198973+ + 1198621198742minus3 + 16119874119867minus + 41198672119874 997888rarr

11987211989261198601198972 (119874119867)16 1198621198743 sdot 41198672119874(6)




10mm

a1 b1 c1 d1

a2 b2 c2 d2

a3 b3 c3 d3

a4 b4 c4 d4

a5 b5 c5 d5








4 Conclusion



20m

(a)

20m

(b)

20m

(c)

LDH

-phase

eutectic phase

-phase

Time 10min

Time 20min

Time 30min

2m

(d)



Data Availability




Acknowledgments


References










































3 CO2minus




















Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





10m

AZ91D

(a)

10m

CO2_24h

(b)

10m

CO2_2hpH115_2h

(c)

10m

CO2_3MPa_05h

(d)


10 20 30 40 50

Inte

nsity

(au

)

2 (deg)

LDHsMgMg17Al12

CCO2_24h

BCO2_2h_2h

ACO2_3MPa_05h

DAZ91D



1E-7 1E-6 1E-5 1E-4 1E-3minus155

minus150

minus145

minus140

minus135

minus130

minus125

E SHE

(V)

ab

cd

ab

cd

AZ91DCO2_24h


i (A∙ cm2)




0 10 20 30 40 50

00

05

10

15

20

hydr

ogen

evol

utio

n (m

lcm

2 )

Time (h)

a

b

c

d

ab

cd

AZ91DCO2_24h









119872119892 minus 2119890minus 997888rarr 1198721198922+ (1)

119860119897 minus 3119890minus 997888rarr 1198601198973+ (2)

2119867+ + 2119890minus 997888rarr 1198672 (119892) (3)

11986721198621198743 997888rarr 119867119862119874minus

3 + 119867+ (4)

11986721198621198743 997888rarr 1198621198742minus

3 + 2119867+ (5)

61198721198922+ + 21198601198973+ + 1198621198742minus3 + 16119874119867minus + 41198672119874 997888rarr

11987211989261198601198972 (119874119867)16 1198621198743 sdot 41198672119874(6)




10mm

a1 b1 c1 d1

a2 b2 c2 d2

a3 b3 c3 d3

a4 b4 c4 d4

a5 b5 c5 d5








4 Conclusion



20m

(a)

20m

(b)

20m

(c)

LDH

-phase

eutectic phase

-phase

Time 10min

Time 20min

Time 30min

2m

(d)



Data Availability




Acknowledgments


References










































3 CO2minus




















Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





0 10 20 30 40 50

00

05

10

15

20

hydr

ogen

evol

utio

n (m

lcm

2 )

Time (h)

a

b

c

d

ab

cd

AZ91DCO2_24h









119872119892 minus 2119890minus 997888rarr 1198721198922+ (1)

119860119897 minus 3119890minus 997888rarr 1198601198973+ (2)

2119867+ + 2119890minus 997888rarr 1198672 (119892) (3)

11986721198621198743 997888rarr 119867119862119874minus

3 + 119867+ (4)

11986721198621198743 997888rarr 1198621198742minus

3 + 2119867+ (5)

61198721198922+ + 21198601198973+ + 1198621198742minus3 + 16119874119867minus + 41198672119874 997888rarr

11987211989261198601198972 (119874119867)16 1198621198743 sdot 41198672119874(6)




10mm

a1 b1 c1 d1

a2 b2 c2 d2

a3 b3 c3 d3

a4 b4 c4 d4

a5 b5 c5 d5








4 Conclusion



20m

(a)

20m

(b)

20m

(c)

LDH

-phase

eutectic phase

-phase

Time 10min

Time 20min

Time 30min

2m

(d)



Data Availability




Acknowledgments


References










































3 CO2minus




















Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





10mm

a1 b1 c1 d1

a2 b2 c2 d2

a3 b3 c3 d3

a4 b4 c4 d4

a5 b5 c5 d5








4 Conclusion



20m

(a)

20m

(b)

20m

(c)

LDH

-phase

eutectic phase

-phase

Time 10min

Time 20min

Time 30min

2m

(d)



Data Availability




Acknowledgments


References










































3 CO2minus




















Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





20m

(a)

20m

(b)

20m

(c)

LDH

-phase

eutectic phase

-phase

Time 10min

Time 20min

Time 30min

2m

(d)



Data Availability




Acknowledgments


References










































3 CO2minus




















Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls



































3 CO2minus




















Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls



















Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls




anticorrosion performance of ldh coating prepared by

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