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Dopant effects in polyaniline inhibition of corrosion-driven organic coating cathodic delamination on iron

TitleDopant effects in polyaniline inhibition of corrosion-driven organic coating cathodic delamination on iron
Publication TypeJournal Article
Year of Publication2006
AuthorsWilliams, G., Gabriel A., Cook A., and McMurray H. N.
JournalJournal of the Electrochemical Society
Volume153
PaginationB425-B433
KeywordsAtmospheric humidity, Cathodes, Delamination, Dopant effects, Doping (additives), Electrochemical corrosion, Electrostatic coatings, Emeraldine, Iron compounds, Organic coatings, Polyaniline, Reaction kinetics, Scanning Kelvin probe, Solutions, Thin films
Abstract Coatings comprising various volume fractions of participate polyaniline dispersed in a polyvinylbutyral binder are applied to iron substrates. A scanning Kelvin probe is used to measure substrate potentials in humid air and follow corrosion-driven coating delamination (cathodic disbondment) when 5% w/v (0.86 M) aqueous NaCl contacts a coating defect. Emeraldine base has no effect on substrate potential or delamination kinetics. Emeraldine salts (ES) doped using p-toluenesulfonic (HpTS), camphorsulfonic (HCS), phosphoric (H 3PO4), and phenylphosphonic (H2PP) acids increase substrate potentials by up to 0.36 V and inhibit delamination with efficiency order of HpTS < HCS < H3PO4 ≪ H 2PP. Dopant salts added to the corrosive electrolyte do not inhibit delamination. It is proposed that inhibition arises primarily from cathodic O2 reduction becoming relocated from the ennobled substrate onto the ES coating. However, Fe3(PO4)2 and FePP salt films formed at the ES-substrate interface also contribute by hindering interfacial electron transfer. © 2006 The Electrochemical Society. All rights reserved.
URLhttp://www.scopus.com/inward/record.url?eid=2-s2.0-33748413325&partnerID=40&md5=0f8f7057469c4f397656a3cc8fc51f1d
DOI10.1149/1.2229280

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