Corrosion Behavior of Mild Steel in Hydrochloric Acid Solutions.pdf

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1、Int.J.Electrochem.Sci.,3(2008)806-818


www.electrochemsci.orgCorrosionBehaviorofMildSteelinHydrochloricAcidSolutions*EhteramA.Noor,AishaH.Al-MoubarakiKingAbdEl-AzizUniversity,Girls’CollegeofEducation,DepartmentofChemistry,Jeddah-9470,KSA*E-mail:m7o7o7n@hotmail.c

2、omReceived:9April2008/Accepted:6May2008/Published:29May2008Thecorrosionbehaviourandmechanismformildsteelinhydrochloricacidsolutionswasstudiedbychemical(hydrogenevolution,HE&massloss,ML)andelectrochemical(electrochemicalimpedanceospectroscopy&potentiodynamicpolarization)methodsat25C.Thechemicalresul

3、tsrevealedthatmildsteelcorrodesinHClsolutionswitharectionconstantof0.56andthecorrosionrateincreaseswiththeincreaseinacidconcentration.MicrostructuralstudiesformildsteelafterimmersioninHClsolutionsofdifferentconcentrationsshowedgeneralandpittingcorrosionandthelatterbecomesmorepronouncedathigherlevel

4、ofHClconcentration.Accordingly,itwasfoundthatRctvaluedecreaseswhilebothCdlandicorr.valuesincreasewithincreasingHClconcentration.PDPresultsrevealedthatthesteeldissolutionisanodicallycontrolled.EstimationoftheratioZ/vsfromPDPdataindicatedthatmildsteeldissolutionoccursviamultistepmechanism.Thismechani

5、sminvolvestwostepseachofthemischaracterizedbyoneelectronreleaseandoneofthemistheratedeterminingstep.Therate-determiningstepmayinvolveadsorbed[FeOH]adsand/or[FeClOH]adsgroups.Keywords:Mildsteel;Corrosion;Hydrochloricacid;Impedance;Polarization1.INTRODUCTIONMildsteelisoneofthemajorconstructionmateria

6、ls,whichisextensivelyusedinchemicalandalliedindustriesforthehandlingofacid,alkaliandsaltsolutions[1].Hydrochloricacidisthemostdifficultofthecommonacidstohandlefromthestandpointsofcorrosionandmaterialsofconstructions.Extremecareisrequiredintheselectionofmaterialstohandletheacidbyitself,eveninrelativ

7、elydiluteconcentrationsorinprocesssolutionscontainingappreciableamountofhydrochloricacid.Thisacidisverycorrosivetomostofthecommonmetalsandalloys[2].Theaimofthisworkistoinvestigatethecorrosionbehaviourandmec