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Abstract
Polyelectrolytes have been proposed as promising systems for the potection of stainless steels and for biomedical and drug release applications. Multilayer nanofilms with varying anion acidity were deposited on AISI316L stainless steel. The cationic polyelectrolyte was polyallylamine hydrochloride (PAH) whereas the anionic polyelectrolytes with increasing acidity were polyacrylic acid (PAA), polystyrene sulphonate-co-maleic acid and polystyrene sulphonate (PSS). Potentiodynamic polarisation showed an increase in corrosion potential E corr upon coating with multilayer nanofilms and a corresponding decrease in corrosion current. Transient currents were observed upon application of PSS due to its high acidic strength although it showed better pit recovery characteristics as shown in cyclic polarisation experiments. Constant potential experiments at 700 mV v. Ag/AgCl for 12 h showed a suppressed current by 50% for the PAH/PSS coated steel compared to the uncoated specimen. The SEM images showed the existence of agglomerates, uncovered areas and corrosion products underneath channels on the coating.