Anodizing Steel in basic SolutionsCapstone ProjectVaibhav Gupta - 1110803!adhur "agai - 11108013#ntroduction "are Steels rust $hen e%posed to neutral p& $ater' salt$ater or high hu(idit) air* +he proble( $ith iron is that the o%ide ,or(ed b) o%idation does not -r(l) adhere to the sur,ace o, the (etal and .a/es o0 easil) causing 1pitting1* 2%tensive pitting eventuall) causes structural $ea/ness and disintegration o, the (etal* Due to atmospheric oxidation Iron forms faky and non adherent rust consisting o, lepidocrocite 3ga((a-4e55&6 and goethite 3alpha-4e55&6* Our project aims to grow an adherentoxide (magnetite) layer' a light bro$n o%ide' or a se(i adherent dichroic (agnetite la)er on di0erent t)pes o, steel* +he dichroic o%ide la)ers e%hibit the di0erent colors o, the rainbo$ depending on the thic/ness o, the la)er and the vie$ing angle* +hese anodized o%ides $ill provide corrosion protection and and the) are also a suitable substrate ,or bonding organic coatings* 7iterature revie$ Steel can gro$ a passive o%ide -l( in caustic solutions and in concentrated nitric acid' but not in neutral $ater' as do alu(inu(' chro(iu(' and titaniu(* +he high te(perature o%ide on steel is generall) a loose' dendritic gro$th that tends to spall and is not a protective barrier* &o$ever' +here are (an) process that ,or( adherent thic/ o%idesbut the) all re8uire ver) high te(peratures* +he $eathering steels can also gro$ a protective o%ide during at(ospheric e%posure* +he $eathering steels' AS+! A9:9 steel $ith high Cu and P and AS+! A;88 steel $ith high Cu' Cr' and 1:;@C and all o, his coatings $ere a loose' bro$n o%ide that could be $iped o0 to reveal an adherent' bro$n o%ide*3* "a%ter and Gor/ie$icz (ade a re,erence to Aanodized steelB in 1=8?' but their anodizing process $as in a hot borate solution that could gro$ an o%ide onl) 10 n( thic/* +he purpose o, their treat(ent $as to passivate the steel sur,ace so the) could then i(age an) ,atigue crac/s b) using a potassiu( iodide gel*!ethodolog)+he opti(u( anodization setup is sho$n in -gure* +he steel to be anodized is connected to the positive ter(inal the anode o, the po$er suppl) and a steel counter electrode is connected to the negative ter(inal the cathode* +he tests areconducted using D5& and 0*0= E' !n - 0*33E '