Research Article Influence of Heat Treatment on the Corrosion of …downloads.hindawi.com/journals/jchem/2013/587514.pdf · 2019-07-31 · Influence of Heat Treatment on the Corrosion

Hindawi Publishing CorporationJournal of ChemistryVolume 2013 Article ID 587514 7 pageshttpdxdoiorg1011552013587514

Research ArticleInfluence of Heat Treatment on the Corrosion of MicroalloyedSteel in Sodium Chloride Solution

Asiful Hossain Seikh

Centre of Excellence for Research in Engineering Materials King Saud University PO Box 800 Riyadh 11421 Saudi Arabia

Correspondence should be addressed to Asiful Hossain Seikh asifulsgmailcom

Received 28 May 2013 Revised 19 September 2013 Accepted 19 September 2013

Academic Editor Hassan Arida

Copyright copy 2013 Asiful Hossain SeikhThis is an open access article distributed under theCreative CommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Microalloyed Steels find wide application in car bodies and other engineering parts because of its high strength as well as highductility Very fine grained microstructure is the reason behind the combination of strength and ductility It has been reported thatrepeated quenching leads to further refining of microstructure In the present investigation corrosion resistance property of E34microalloy steel has been studied in 35 NaCl solution in different microstructural conditions such as the as rolled one and threerepeated quenched conditions Weight loss potentiodynamic polarization method and electrochemical impedance spectroscopy(EIS) techniques have been used To reveal the corrosion resistance of different treated steels some significant characterizationparameters such as 119864corr 119868corr 119877119901 and 119877ct in linear polarization and EIS curves were analyzed and compared It is found that withrepeated recrystallization grains become finer and corrosion rate increases suggesting that a compromise has to strike betweenhigh mechanical property and corrosion rate

1 Introduction

Microalloyed Steels finds wide applications including auto-mobile frames gas transmission pipelines ship plates bridgebeams and electrical power transmission poles because ofits high strength as well as high ductility Microalloyedpipeline steels are extensively used in the oil and gas industryand have severe mechanical requirements for sour serviceapplications and deep water gas wells Microalloyed steelhas a ferritic matrix that is of a mild steel but with anextremely fine grained structure Very fine grain structureof this steel is due to the combination of high strength andductility This combination is given through the additionof microalloying elements such as Mo Ti V Ni and Nband also due to thermomechanical heat treatments [1ndash3]Alloying additions of these alloying elements of the order ofmicroadditions brings this refinement in the microstructureThese microalloying elements improve the strength proper-ties due to fine precipitation within the grains in additionto the solute drag effect in the hardenability of the steelsdue to the reduction of grain coarsening during heating Onthe other hand it has been reported that without change in

other microconstitutional properties the grain refinement offerritic microalloyed steels is done by repeated quenchingfrom a temperature just below the lower critical temperaturethat is in the ferritic region as reported in the literature [4 5]Corrosion behavior of steel and the effects of microstructureon such behavior are still an open field for investigationto correlate the metallurgical concept with the corrosionparameters Due to environmental and economical effectsthe steel corrosion is considered as amajor industrial problemthat costs hundreds of billions of dollars [6] Corrosionof structural elements is a major issue for any industrydue to the chemical environment of chemical processingSeveral industries used acid solutions for cleaning picklingdescaling and acidizing processes by which steels come incontact with acids Only few authors [7ndash9] have investigatedthe influence of heat treatment on the corrosion behavior ofsteel in different solution

In the present study corrosion property of as rolledand repeatedly quenched microalloyed steels in 35NaClsolution has been studied by weight loss potentiodynamicpolarization method and electrochemical impedance spec-troscopy (EIS) techniques

2 Journal of Chemistry

2 Experimental

21 Materials The materials are commonly called Nb-bearing commercial microalloyed steel E-34 grades withchemical composition (weight) Fe 0060C 057Mn 0008S0012P 0020Si 0055Al and 0012Nb

22 Heat Treatment Four numbers of square-section speci-men strips of size (10mm times 10mm times 5mm) were cut out withthe help of a hack saw from the hot rolled steel plate keepingthe long axis of the strips parallel to the rolling directionas determined from the metallographic analysis of the asreceived microalloyed steel plate and were prepared for heattreatment after grinding in a wheel

For grain refinement of the ferritic microalloyed steelsrepeated quench from a temperature just below the lowercritical temperature was adopted [4] In the heat treatmentfirstly set the furnace at a temperature of 600∘C just belowthe lower critical temperature Out of 4 samples 3 sampleswere kept in the furnace at a temperature of 600∘C justbelow the lower critical temperature and heated at thescheduled temperature for 45 minutes to get uniform heatingof the entire cross-section After that the samples were takenoutside and immediately put into a water bath The sampleswere quenched until the temperature came down to roomtemperature Now 1 sample was taken out and 2 others wereheat treated in similar way out of which 1 was taken outand another 1 was treated again in same way During coolingin the quenching bath continuous stirring of the bath hasbeen carried out in all the treatment cycles for uniform heattransfer

All heat treatment cycles were carried out in a MuffleFurnace coupled with a proportional temperature controllerwith an accuracy level of plusmn20∘CThe furnace atmosphere wasnot controlled

23 Sample Preparation One of the surfaces of each of themetallographic specimens as received (designates as AR)first quench (designates as Q1) second quench (designates asQ2) and third quench (designates as Q3) of each grade wasgroundedmechanically on the silicon carbide abrasive paperssequentially on 60 120 240 320 400 and 600 grit siliconcarbide papers and polished on a Selvyt cloth using coarseand fine Geosyn-Grade I slurry of Al2O3 Specimens werecleaned washed by water and then by alcohol and dried Allthe polished specimens were etched using 2 nital solution(2 HNO3 in Methanol) With these polished and etchedsamples optical microscopy grain size measurement andhardness testing were carried out

24 Optical Microscopy Grain Size Measurement and Hard-ness Testing The etched specimens were tested one byone using an optical microscope The photographs of themicrostructure were taken with help of a Camera fitted witha microscope

The grain size of each specimen was measured by usinga real image analysis with the help of an image analyzingsoftware Biovis Material Plus-version 13

Vickers hardness of the metallographic specimens wascarried out in a standard Vickers hardness testing machineusing square-base diamond pyramid as the indenter anda load of 30 kg as per ASTM Standard E92-72 Tests werecarried out at least in three different positions on the polishedsurface of the specimens and the average Vickers hardnessvalue was reported

25 Solution Preparation Experimentswere done in stagnant35NaCl solution The solution was prepared from analyt-ical grade reagents and distilled water While the electrolytesolutions were in equilibriumwith the atmosphere all exper-iments were carried out under thermostatic conditions 25∘C(plusmn01∘C)

26 Experimental Procedure

261 Weight Loss Measurement Microalloyed steel speci-mens of dimension 10mm times 10mm times 5mmwere cut abradedwith various grades of silicon carbide papers (200 400 600800 and 1000) The exact area and thickness of each couponwere measured and washed with distilled water containingdetergent Specimenswere then degreased againwith acetoneand finally dried After weighing with sensitive electronicbalance specimens were immersed in 50mL 35NaClsolutions (nondeaerated) at room temperature Weight lossof metal specimens was noted at every 24 h time interval forfive days The experiments were carried out in duplicate andthe average values were reported We carried out immersiontest in accordance with ASTM G31-72 The corrosion rate (])is calculated by the following equation [10]

] =119882

119878119905 (1)

where W is the average weight loss of coupon 119878 is the totalarea of specimen and t is the time of treatment

262 Linear Polarization and EIS Measurement Linearpolarization and the EIS were performed in a conventionalthree-electrode cell in which AgAgCl was the referenceelectrode platinum foil was the counter electrode and thesteel strip was the working electrode (WE) All potentialsquoted in this paper were referred to the AgAgCl

As introduced before the strips of E-34 grade withdifferently treated conditions were used as working electrodeSpecimens were machined into a cuboidal form with anexposed area 1 cm2 An insulated copper wire was securedto one of the surfaces of each steel specimen with solder atlow temperature The specimens were mounted with epoxideresin in such a way that only the other flat surface contactedwith the solution This flat surface of each specimen was pol-ished mechanically in a graded emery paper and final finishwas given on a polishing wheel using alumina powder Thepolished surface was then thoroughly washed and digressedin ethanol before use and dried at room temperature

Corrosion tests were carried out by using an AutolabPotentiostat (PGSTAT20 computer controlled) operated bythe general purpose electrochemical software (GPES) version

Journal of Chemistry 3

49 The free corrosion potential (versus AgAgCl) wasfollowed after immersing the working electrode in the testsolution until the potential stabilized within plusmn1mV This wasfollowed by electrochemical impedance spectroscopy testEIS data were recorded for the steel specimens at corrosionpotentials (119864corr) after 60mins immersion in the test solutionThe frequency was scanned from 100KHz to 100mHz withan ac wave of plusmn5mV peak-to-peak overlaid on a dc biaspotential to get Nyquist and bode plots The best equivalentcircuit of Nyquist plots was calculated by fit and simulationmethod The linear potentiodynamic polarization curveswere obtained by scanning the potential in the forwarddirection from minus01 to 01 V against AgAgCl at a scan rateof 1mVs

All the electrochemical experiments were recorded afterimmersion of the electrode in the test solution for 60minsat a temperature of (25 plusmn 1)∘C Fresh solution and fresh steelsamples were used after each sweep For each experimentalcondition two to three measurements were performed toensure the reliability and reproducibility of the data

3 Results and Discussions

31 Metallographic Studies of the Microalloyed Steel Figure 1shows the microstructure of (a) as received (b) first quench(c) second quench and (d) third quenched BSK 46 (themagnifications for all specimens were 4 times 40x) The variationof the grain size number with the change of the quenchingtemperature is also listed in Table 1 It is clearly seen fromFigure 1 that the grain size is bigger for the as received sampleand gets finer with quenching and further with repeating thenumber of quenching up to the third time The numericalvalues of the grain size recorded in Table 1 in additionto the images shown in Figure 1 confirm that the ferriticgrain size decreases with repeating the quench from first tothird quench Here the ASTM grain size number of the asreceived sample was reported to be 100 increased due to firstquenching to 105 and further increased to 108 for secondquenching and finally recorded the highest value 110 withrepeating the process to the third quenching This is becausethe repeated quenching leads to repeated recrystallizationwhich in turn leads to producing new grains at the expenseof others and a coarse grained material (as rolled) replacesthe fine grained recrystallized structure This concludes thatincreasing the repeated quenching increases the ASTM grainsize number and therefore decreases the grain size

The variation of the Vickers hardness number (VHN)for the test specimens with the number of the repeatedquenching is listed in Table 2 It is shown from Table 2 thatthe hardness values for the as received E-34 sample recorded146 VHN This value increased to 167 VHN 170 VHN and172 VHN when the repeated quenching for the tested speci-men was increased from first quench to second quench andfurther to third quench sample respectively This increase inthe hardness values with increasing the repeated quenching isattributed to the grain refinement of the ferritic microalloyedE-34 steel So from this it can be concluded that due to

Table 1 ASTM grain size number for the tested specimens

As received First quench Second quench Third quench100 105 108 110

Table 2 Vickers hardness number (VHN) for the test specimens


Table 3 Corrosion rate in (mg cmminus2 hminus1) data obtained fromweightloss measurements for different microalloy steel in 35 NaClsolutions at room temperature

Corrosion rates in (mg cmminus2 hminus1) at 35 NaClAs received First quench Second quench Third quench633 972 1121 1384

repeated quenching grain refinement of ferritic microalloyedsteels can be achieved

32 Weight Loss Measurements Table 3 presents the valuesof the corrosion rates (in mg cmminus2 hminus1) derived from weightlossmeasurements for differentmicroalloy steel after 5 hoursof immersion in 35 NaCl solutions at room temperatureIt is observed that the samples lose weight with increasingexposure time trend of weight loss is increasing order ofas received first quench second quench and third quenchsamples The observed increase in cumulative weight lossof the samples at constant temperature agrees with theobservation earlier made that corrosion rate at constanttemperature increases with increasing exposure time whilethe observed variation in the weight loss of the sample maybe attributed to difference in the samples grain size [11] It wasequally revealed that heat treatment affects rate of corrosionand posited that the bigger the grains of a material the moreare its resistance to corrosion [12] Hence the as receivedsample with the biggest grain size distribution revealed lessweight loss as compared to the repeated quenched samples

33 Potentiodynamic Polarization Measurements The polar-ization curves for microalloy steel specimens (As received(AR) first quench (Q1) second quench (Q2) and thirdquench (Q3)) in 35 NaCl at room temperature are shownin Figure 2 Polarization parameters obtained from thecurves are as shown in Table 4 These parameters includethe values of corrosion current densities (119868corr) corrosionpotential (119864corr) cathodic Tafel slope (119887119888) anodic Tafel slope(119887119886) and polarization resistance (119877119901) The corrosion currentdensity 119868corr was determined graphically by extrapolating thecathodic and anodic Tafel slopes to the119864corr (versusAgAgCl)as shown in Figure 3 in case of as received (AR) sampleFrom the slope analysis of the linear polarization curves inthe vicinity of corrosion potential the values of polarizationresistance (119877119901) in 35 NaCl solution were obtained

From polarization data it is found that 119864corr (versusAgAgCl) values shifted towards more cathodic (negative)


(a) (b)

(c) (d)

Figure 1 The microstructure of (a) as received (b) first quench (c) second quench and (d) third quenched E-34 all magnifications were4times 40x

Table 4 Potentiodynamic polarization parameters of microalloy steel samples in 35 NaCl at room temperature

Tafel data Linear polarization data119887119886mVdecade 119887119888mVdecade 119864corr mV 119868corr 120583A 119877119901 Ω

As received 6468 3635 minus539 23645 9739First quench 6062 5048 minus629 48089 7586Second quench 8543 5487 minus664 50893 6894Third quench 6264 4937 minus692 11086 5946

minus09 minus08 minus07 minus06 minus05 minus04Potential applied (V)

Log

curr

ent (

A)

ARQ1Q2Q3100E minus 07

100E minus 06

100E minus 05

100E minus 04

100E minus 03

100E minus 02

Figure 2 Potentiodynamic polarization curves for microalloy steelsamples in 35NaCl at room temperature (AR-as received Q1-firstquench Q2-second quench and Q3-third quench)

region and 119868corr values increases as we go for repeatedquenching Grain refinement achieved in repeated quenchingrenders greater anodic area than coarser grained structure

AR

minus08 minus07 minus06 minus05 minus04Potential applied (V)

Log

curr

ent (

A)

100E minus 07

100E minus 06

100E minus 05

100E minus 04

100E minus 03

100E minus 02

Figure 3 Determination of polarization parameters by Tafel extrap-olation method (eg as received sample)

[6] Hence corrosion rate increases and polarization resis-tance (119877119901) decreases due to repeated quenching

In steel when oxygen is present iron is oxidized atthe anodic site and releases electrons (see (2)) At the


cathode oxygen combines with moisture and the electronsare released at the anode to form hydroxyl ions (see (3))

Fe 997888rarr Fe2+ + 2eminus (2)

1

2O2 +H2O + 2e

minus997888rarr 2OHminus (3)

In the presence of chlorides iron at the anode is oxidized asbefore (see (2)) and the ferrous ions react with chloride ionsto form a soluble iron-chloride complex (see (4)) The iron-chloride complex reacts with hydroxyl ions and forms ferroushydroxide (see (5)) which is a greenish black product

Fe2+ + 2Clminus 997888rarr [FeCl complex]+ (4)

[FeCl complex]+ + 2OHminus 997888rarr Fe(OH)2 + Clminus (5)

4Fe(OH)2 + 2H2O +O2 997888rarr 4Fe(OH)3 (6)

2Fe(OH)3 997888rarr Fe2O3 + 3H2O (7)

The ferrous hydroxide is oxidized to ferric hydroxide thatin turn dehydrates to form ferric oxide as shown in (6) and(7) At the cathode hydroxyl ions are formed when oxygencombines with moisture and the electrons are releasedat the anode as before (see (3)) As demonstrated by (4)and (5) the chloride ions are not consumed and remainavailable to continue contributing to corrosion Chlorideattack on steel usually occurs as pitting corrosion Pittingwill continue to increase if the chloride content exceeds aspecific concentration This chloride threshold is believed tobe dependent on the concentration of hydroxyl ions [13]

Potentiodynamic polarization curves in Figure 2 showno sharp slope in the anodic range meaning that no passivefilms are formed on the metal surface [14] According to thecorrosion theory the shift in the cathodic curves reveals thatthe corrosion process is mainly accelerated by the cathodicreactions

34 Electrochemical Impedance Spectroscopy (EIS) Measure-ments The corrosion response of microalloy steel specimensin 35 NaCl solution has been investigated using electro-chemical impedance spectroscopy at room temperature andthe Bode and Nyquist plots are represented in Figure 4 Itis seen from this Figure that the shapes of Nyquist plots forthe as received as well as quenched specimens are similarat each concentration with one depressed semicircle Ascan be seen from Figure 4 the Nyquist plots do not yieldperfect semicircles as expected from the theory of EIS Thedeviation from ideal semicircle was generally attributed to thefrequency dispersion [15] as well as to the inhomogeneitiesof the surface and mass transport resistant [16] It is evidentfrom the plots that the impedance response of as receivedsteel specimens showed a marked difference with that ofquenched samples The capacitance loop intersects with thereal axis at higher and lower frequencies At high frequencyend the intercept corresponds to the solution resistance (119877119904)and at lower frequency end corresponds to the sum of 119877119904 and

Table 5 Electrochemical impedance parameters of microalloy steelsamples in 35 NaCl at room temperature

EIS data119877119904 Ω CPE (1198840) 120583Mho 119899 119877ct Ω

As received 10 1080 0863 775First quench 10 1020 0864 490Second quench 8 859 0815 440Third quench 7 768 0833 340

charge transfer resistance (119877ct) The difference between thetwo values gives 119877ct The value of 119877ct is a measure of electrontransfer across the exposed area of the metal surface and it isinversely proportional to rate of corrosion [17]

Impedance behaviour can be well explained by pureelectric models that could verify and enable to calculatenumerical values corresponding to the physical and chemicalproperties of electrochemical system under examination [18]The simple equivalent circuit that fits to many electrochem-ical systems consisting of a parallel combination of a doublelayer capacitance (119862dl) and the charge transfer resistance (119877ct)corresponding to the corrosion reaction at metalelectrolyteinterface and the solution resistance (119877s) between the work-ing and reference electrode [19 20] To reduce the effectsdue to surface irregularities of metal constant phase element(CPE) is introduced into the circuit instead of a pure doublelayer capacitance which gives more accurate fit [21] as shownin Figure 5

The impedance of CPE can be expressed as

119885CPE =1

1198840

(119895120596)119899 (8)

where 1198840 is the magnitude of CPE n is the exponent (phaseshift) 120596 is the angular frequency and j is the imaginaryunit CPE may be resistance capacitance and inductancedepending upon the values of n [19] In all experiments theobserved value of n ranges between 08 and 10 suggesting thecapacitive response of CPE

The EIS parameters such as 119877ct 119877119904 and CPE are listed inTable 5 indicating that the values of 119877ct are found to decreasewith repeated quenching These observations support theidea that the corrosion of steel is controlled by a chargetransfer process [22] Bode plots shown in Figure 4 indicatesthe presence of one time constant corresponding to onedepressed semicircle that was obtained in case of Nyquistplots

The corrosion resistance calculated from EIS resultsshows the same trend as those obtained from polarizationmeasurements The difference in corrosion resistance of thetwo methods may be due to the different surface status ofthe electrode in two measurements EIS were performedat the rest potential while in polarization measurementsthe electrode potential was polarized to high over potentialnonuniform current distributions resulted from cell geom-etry solution conductivity counter and reference electrodeplacement and so forth will lead to the difference betweenthe electrode area actually undergoing polarization and thetotal area [23]


0

50

100

150

200

250

300

350

0 200 400 600

minusZ998400998400(Ω

)

Z998400 (Ω)

ARQ1

Q2Q3

(a)

700

600

500

400

300

200

100

0

Z(Ω

)

01 0 10 100 1000 10000 100000

Frequency (Hz)

ARQ1

Q2Q3

(b)

Figure 4 Electrochemical Impedance curves (Nyquist and Bode) for microalloy steel samples in 35 NaCl at room temperature (AR-asreceived Q1-first quench Q2-second quench and Q3-third quench)

0

50

100

150

200

250

300

350

0 100 200 300 400 500 600

AR

minusZ998400998400(Ω

)

Z998400 (Ω)

(a)

R = 100Ω

R = 775Ω

Y0 = 108mMhoN = 0863

(b)

Figure 5 Determination of EIS parameters from the equivalent circuit (eg as received sample)

4 Conclusions

The effects of grain refinement on the corrosion of E-34 microalloyed steel in different concentration of NaClsolutions after differentmicrostructural conditions have beeninvestigated Due to repeated quenching from a temper-ature just below the lower critical temperature the grainrefinement of ferritic microalloyed steel has been achievedRepeating the quenching up to three times led to yieldingnew grains at the expense of others and a coarse grainedmaterial (as rolled) is replaced by the fine grained recrystal-lized structure Corrosion rate (119868corr) increases for repeatedquenched samples implies that corrosion rate increases asgrain refinement increases The repeated quenching refinesthe grains which renders greater anodic areas than coarsergrained structure and thus activates the corrosion of steelCorrosion potential (119864corr) moves to more cathodic regionindicates that the corrosion process is mainly accelerated bythe cathodic reactions The corrosion resistance calculated

fromEIS results shows the same trend as those obtained frompolarization measurements Results obtained from weightloss dc polarization and ac impedance techniques are inreasonably good agreement

Acknowledgment

The author extends his appreciation to the Center of Excel-lence for Research in Engineering Materials (CEREM) ofAdvanced Manufacturing Institute King Saud UniversityRiyadh Saudi Arabia for funding the work

References

[1] I A Yakubtsov P Poruks and J D Boyd ldquoMicrostructure andmechanical properties of bainitic low carbon high strength platesteelsrdquoMaterials Science and Engineering A vol 480 no 1-2 pp109ndash116 2008


[2] M-C Zhao K Yang and Y-Y Shan ldquoComparison on strengthand toughness behaviors of microalloyed pipeline steels withacicular ferrite and ultrafine ferriterdquo Materials Letters vol 57no 9-10 pp 1496ndash1500 2003

[3] F Xiao B Liao D Ren Y Shan and K Yang ldquoAcicular fer-ritic microstructure of a low-carbon Mn-Mo-Nb microalloyedpipeline steelrdquo Materials Characterization vol 54 no 4-5 pp305ndash314 2005

[4] B K Panigrahi ldquoProcessing of low carbon steel plate and hotstrip-an overviewrdquo Bulletin of Materials Science vol 24 no 4pp 361ndash371 2001

[5] R Song D Ponge D Raabe J G Speer and D K MatlockldquoOverview of processing microstructure andmechanical prop-erties of ultrafine grained bcc steelsrdquo Materials Science andEngineering A vol 441 no 1-2 pp 1ndash17 2006

[6] G O Oluwadare and O Agbaje ldquoCorrosion of steels in steelreinforced concrete in cassava juicerdquo Journal of Applied Sciencesvol 7 no 17 pp 2474ndash2479 2007

[7] H H Uhlig and W R Revie Corrosion and Corrosion ControlAn Introduction to Corrosion Science and Engineering JohnWiley amp Sons New York NY USA 1985

[8] H Luo Y C Guan and K N Han ldquoInhibition of mild steelcorrosion by sodium dodecyl benzene sulfonate and sodiumoleate in acidic solutionsrdquo Corrosion vol 54 no 8 pp 619ndash6271998

[9] H J Cleary andND Greene ldquoCorrosion properties of iron andsteelrdquo Corrosion Science vol 7 no 12 pp 821ndash831 1967

[10] X Li S Deng H Fu G Mu and N Zhao ldquoSynergism betweenrare earth cerium(IV) ion and vanillin on the corrosion of steelin H2SO4 solution weight loss electrochemical UV-vis FTIRXPS and AFM approachesrdquo Applied Surface Science vol 254no 17 pp 5574ndash5586 2008

[11] D TOloruntobaOOOluwole andEOOguntade ldquoCompar-ative study of corrosion behaviour of galvanized steel and coatedAl 3103 roofing sheets in carbonate and chloride environmentsrdquoMaterials and Design vol 30 no 4 pp 1371ndash1376 2009

[12] G H Aydogdu and M K Aydinol ldquoDetermination of suscep-tibility to intergranular corrosion and electrochemical reacti-vation behaviour of AISI 316L type stainless steelrdquo CorrosionScience vol 48 no 11 pp 3565ndash3583 2006

[13] D A Hausmann ldquoSteel corrosion in concreterdquo MaterialsProtection vol 6 pp 19ndash23 1967

[14] S John K Mohammad Ali and A Joseph ldquoElectrochemicalsurface analytical and quantum chemical studies on schiffbases of 4-amino-4H-124-triazole-35-dimethanol (ATD) incorrosion protection of aluminium in 1N HNO3rdquo Bulletin ofMaterials Science vol 34 no 6 pp 1245ndash1256 2011

[15] H H Hassan E Abdelghani and M A Amin ldquoInhibition ofmild steel corrosion in hydrochloric acid solution by triazolederivatives Part I Polarization and EIS studiesrdquo ElectrochimicaActa vol 52 no 22 pp 6359ndash6366 2007

[16] P Bommersbach C Alemany-Dumont J P Millet and BNormand ldquoFormation and behaviour study of an environment-friendly corrosion inhibitor by electrochemical methodsrdquo Elec-trochimica Acta vol 51 no 6 pp 1076ndash1084 2005

[17] I L Rosenfield Corrosion Inhibitors McGraw-Hill New YorkNY USA 1981

[18] A Subramania A R Sathiya Priya and V S MuralidharanldquoDevelopment of novel acidizing inhibitors for carbon steelcorrosion in 15 boiling hydrochloric acidrdquo Corrosion vol 64no 6 pp 541ndash552 2008

[19] A K Singh S K Shukla M Singh and M A QuraishildquoInhibitive effect of ceftazidime on corrosion of mild steel inhydrochloric acid solutionrdquo Materials Chemistry and Physicsvol 129 no 1-2 pp 68ndash76 2011

[20] M El Azhar B Mernari M Traisnel F Bentiss and MLagrenee ldquoCorrosion inhibition of mild steel by the new classof inhibitors [25-bis(n-pyridyl)-134-thiadiazoles] in acidicmediardquo Corrosion Science vol 43 no 12 pp 2229ndash2238 2001

[21] J R Macdonald W B Johnson and J R Macdonald Theoryin Impedance Spectroscopy John Wiley amp Sons New York NYUSA 1987

[22] H Wang X Wang H Wang L Wang and A Liu ldquoDFT studyof new bipyrazole derivatives and their potential activity ascorrosion inhibitorsrdquo Journal of Molecular Modeling vol 13 no1 pp 147ndash153 2007

[23] A Raman and P Labine Reviews on Corrosion Inhibitor Scienceand Technology vol 1 NACE Houston Tex USA 1986

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2 Experimental

21 Materials The materials are commonly called Nb-bearing commercial microalloyed steel E-34 grades withchemical composition (weight) Fe 0060C 057Mn 0008S0012P 0020Si 0055Al and 0012Nb

22 Heat Treatment Four numbers of square-section speci-men strips of size (10mm times 10mm times 5mm) were cut out withthe help of a hack saw from the hot rolled steel plate keepingthe long axis of the strips parallel to the rolling directionas determined from the metallographic analysis of the asreceived microalloyed steel plate and were prepared for heattreatment after grinding in a wheel

For grain refinement of the ferritic microalloyed steelsrepeated quench from a temperature just below the lowercritical temperature was adopted [4] In the heat treatmentfirstly set the furnace at a temperature of 600∘C just belowthe lower critical temperature Out of 4 samples 3 sampleswere kept in the furnace at a temperature of 600∘C justbelow the lower critical temperature and heated at thescheduled temperature for 45 minutes to get uniform heatingof the entire cross-section After that the samples were takenoutside and immediately put into a water bath The sampleswere quenched until the temperature came down to roomtemperature Now 1 sample was taken out and 2 others wereheat treated in similar way out of which 1 was taken outand another 1 was treated again in same way During coolingin the quenching bath continuous stirring of the bath hasbeen carried out in all the treatment cycles for uniform heattransfer

All heat treatment cycles were carried out in a MuffleFurnace coupled with a proportional temperature controllerwith an accuracy level of plusmn20∘CThe furnace atmosphere wasnot controlled

23 Sample Preparation One of the surfaces of each of themetallographic specimens as received (designates as AR)first quench (designates as Q1) second quench (designates asQ2) and third quench (designates as Q3) of each grade wasgroundedmechanically on the silicon carbide abrasive paperssequentially on 60 120 240 320 400 and 600 grit siliconcarbide papers and polished on a Selvyt cloth using coarseand fine Geosyn-Grade I slurry of Al2O3 Specimens werecleaned washed by water and then by alcohol and dried Allthe polished specimens were etched using 2 nital solution(2 HNO3 in Methanol) With these polished and etchedsamples optical microscopy grain size measurement andhardness testing were carried out

24 Optical Microscopy Grain Size Measurement and Hard-ness Testing The etched specimens were tested one byone using an optical microscope The photographs of themicrostructure were taken with help of a Camera fitted witha microscope

The grain size of each specimen was measured by usinga real image analysis with the help of an image analyzingsoftware Biovis Material Plus-version 13

Vickers hardness of the metallographic specimens wascarried out in a standard Vickers hardness testing machineusing square-base diamond pyramid as the indenter anda load of 30 kg as per ASTM Standard E92-72 Tests werecarried out at least in three different positions on the polishedsurface of the specimens and the average Vickers hardnessvalue was reported

25 Solution Preparation Experimentswere done in stagnant35NaCl solution The solution was prepared from analyt-ical grade reagents and distilled water While the electrolytesolutions were in equilibriumwith the atmosphere all exper-iments were carried out under thermostatic conditions 25∘C(plusmn01∘C)

26 Experimental Procedure

261 Weight Loss Measurement Microalloyed steel speci-mens of dimension 10mm times 10mm times 5mmwere cut abradedwith various grades of silicon carbide papers (200 400 600800 and 1000) The exact area and thickness of each couponwere measured and washed with distilled water containingdetergent Specimenswere then degreased againwith acetoneand finally dried After weighing with sensitive electronicbalance specimens were immersed in 50mL 35NaClsolutions (nondeaerated) at room temperature Weight lossof metal specimens was noted at every 24 h time interval forfive days The experiments were carried out in duplicate andthe average values were reported We carried out immersiontest in accordance with ASTM G31-72 The corrosion rate (])is calculated by the following equation [10]

] =119882

119878119905 (1)

where W is the average weight loss of coupon 119878 is the totalarea of specimen and t is the time of treatment

262 Linear Polarization and EIS Measurement Linearpolarization and the EIS were performed in a conventionalthree-electrode cell in which AgAgCl was the referenceelectrode platinum foil was the counter electrode and thesteel strip was the working electrode (WE) All potentialsquoted in this paper were referred to the AgAgCl

As introduced before the strips of E-34 grade withdifferently treated conditions were used as working electrodeSpecimens were machined into a cuboidal form with anexposed area 1 cm2 An insulated copper wire was securedto one of the surfaces of each steel specimen with solder atlow temperature The specimens were mounted with epoxideresin in such a way that only the other flat surface contactedwith the solution This flat surface of each specimen was pol-ished mechanically in a graded emery paper and final finishwas given on a polishing wheel using alumina powder Thepolished surface was then thoroughly washed and digressedin ethanol before use and dried at room temperature

Corrosion tests were carried out by using an AutolabPotentiostat (PGSTAT20 computer controlled) operated bythe general purpose electrochemical software (GPES) version


















(a) (b)

(c) (d)






Log

curr

ent (

A)


100E minus 06

100E minus 05

100E minus 04

100E minus 03

100E minus 02



AR


Log

curr

ent (

A)

100E minus 07

100E minus 06

100E minus 05

100E minus 04

100E minus 03

100E minus 02







1

2O2 +H2O + 2e






2Fe(OH)3 997888rarr Fe2O3 + 3H2O (7)










119885CPE =1

1198840

(119895120596)119899 (8)





0

50

100

150

200

250

300

350

0 200 400 600

minusZ998400998400(Ω

)

Z998400 (Ω)

ARQ1

Q2Q3

(a)

700

600

500

400

300

200

100

0

Z(Ω

)

01 0 10 100 1000 10000 100000

Frequency (Hz)

ARQ1

Q2Q3

(b)


0

50

100

150

200

250

300

350

0 100 200 300 400 500 600

AR

minusZ998400998400(Ω

)

Z998400 (Ω)

(a)

R = 100Ω

R = 775Ω

Y0 = 108mMhoN = 0863

(b)


4 Conclusions



Acknowledgment


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


















(a) (b)

(c) (d)






Log

curr

ent (

A)


100E minus 06

100E minus 05

100E minus 04

100E minus 03

100E minus 02



AR


Log

curr

ent (

A)

100E minus 07

100E minus 06

100E minus 05

100E minus 04

100E minus 03

100E minus 02







1

2O2 +H2O + 2e






2Fe(OH)3 997888rarr Fe2O3 + 3H2O (7)










119885CPE =1

1198840

(119895120596)119899 (8)





0

50

100

150

200

250

300

350

0 200 400 600

minusZ998400998400(Ω

)

Z998400 (Ω)

ARQ1

Q2Q3

(a)

700

600

500

400

300

200

100

0

Z(Ω

)

01 0 10 100 1000 10000 100000

Frequency (Hz)

ARQ1

Q2Q3

(b)


0

50

100

150

200

250

300

350

0 100 200 300 400 500 600

AR

minusZ998400998400(Ω

)

Z998400 (Ω)

(a)

R = 100Ω

R = 775Ω

Y0 = 108mMhoN = 0863

(b)


4 Conclusions



Acknowledgment


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(a) (b)

(c) (d)






Log

curr

ent (

A)


100E minus 06

100E minus 05

100E minus 04

100E minus 03

100E minus 02



AR


Log

curr

ent (

A)

100E minus 07

100E minus 06

100E minus 05

100E minus 04

100E minus 03

100E minus 02







1

2O2 +H2O + 2e






2Fe(OH)3 997888rarr Fe2O3 + 3H2O (7)










119885CPE =1

1198840

(119895120596)119899 (8)





0

50

100

150

200

250

300

350

0 200 400 600

minusZ998400998400(Ω

)

Z998400 (Ω)

ARQ1

Q2Q3

(a)

700

600

500

400

300

200

100

0

Z(Ω

)

01 0 10 100 1000 10000 100000

Frequency (Hz)

ARQ1

Q2Q3

(b)


0

50

100

150

200

250

300

350

0 100 200 300 400 500 600

AR

minusZ998400998400(Ω

)

Z998400 (Ω)

(a)

R = 100Ω

R = 775Ω

Y0 = 108mMhoN = 0863

(b)


4 Conclusions



Acknowledgment


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




1

2O2 +H2O + 2e






2Fe(OH)3 997888rarr Fe2O3 + 3H2O (7)










119885CPE =1

1198840

(119895120596)119899 (8)





0

50

100

150

200

250

300

350

0 200 400 600

minusZ998400998400(Ω

)

Z998400 (Ω)

ARQ1

Q2Q3

(a)

700

600

500

400

300

200

100

0

Z(Ω

)

01 0 10 100 1000 10000 100000

Frequency (Hz)

ARQ1

Q2Q3

(b)


0

50

100

150

200

250

300

350

0 100 200 300 400 500 600

AR

minusZ998400998400(Ω

)

Z998400 (Ω)

(a)

R = 100Ω

R = 775Ω

Y0 = 108mMhoN = 0863

(b)


4 Conclusions



Acknowledgment


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0

50

100

150

200

250

300

350

0 200 400 600

minusZ998400998400(Ω

)

Z998400 (Ω)

ARQ1

Q2Q3

(a)

700

600

500

400

300

200

100

0

Z(Ω

)

01 0 10 100 1000 10000 100000

Frequency (Hz)

ARQ1

Q2Q3

(b)


0

50

100

150

200

250

300

350

0 100 200 300 400 500 600

AR

minusZ998400998400(Ω

)

Z998400 (Ω)

(a)

R = 100Ω

R = 775Ω

Y0 = 108mMhoN = 0863

(b)


4 Conclusions



Acknowledgment


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Documents

Research Article Influence of Heat Treatment on the Corrosion of …downloads.hindawi.com/journals/jchem/2013/587514.pdf · 2019-07-31 · Influence of Heat Treatment on the Corrosion