Effect of Al and Ce oxide layers electrodeposited on OC4004 stainless steel on its corrosion characteristics in acid media

Protective effect in sulfuric acid media of alumina and ceria oxide layers electrodeposited on stainless steel

“…In comparison with the case of oxidizing HNO 3 medium [1], in H 2 SO 4 the currents of complete passivation grow higher from 1.1 × 10 − 5 (versus 7.40 × 10 − 6 for 0.1 N HNO 3 ) during the first scanning up to 2.72 × 10 − 2 A.cm − 2 (versus 1.03 × 10 − 5 for 0.1 N HNO 3 ) during the third scanning. The behaviour of the thermally treated steel is similar, whereupon especially impressive is the appearance of strongly expressed "critical currents" of passivation [11] in the anodic polarization curves -after the second scan -at 0.8 V (see the insert in Fig.…”

“…As it was shown earlier [1,2], the electrodeposited layer of ceria influences favourably the variation of the Cr/Fe concentrations ratio in the superficial chromium-containing passive film. These changes, however, depend in a specific way on the conditions of treatment of the system Ce 2 O 3 -CeO 2 /SS (Table 1).…”

“…The juxtaposition of such data with the data, obtained in aggressive media with oxidative effect [1,2] would lead to more explicit conclusions in regard to the nature of their protective effect.…”

“…This positive effect of electrodeposited ceria and alumina layers in nitric acid media was explained in [1,2] by the assumption that they play the role of effective cathodes, which causes a strong shift of the stationary corrosion potential of the steel in positive direction-to the zone of deep anodic passivity, improving its self-passivation. It is necessary to underline, however, that the oxidative component (NO 3 − ) of the corrosive environment, in nitric acid media, might also have a positive contribution in this respect.…”

“…In our previous works it was shown that thin layers of ceria and/or alumina, electrodeposited on stainless steel (SS) from non-aqueous electrolytes, can change/improve substantially the corrosion behaviour of the systems-oxide layer(s)/SS in nitric acid media [1,2]. The interest in studying this effect is determined by some specific applications of stainless steels as construction material for manufacturing catalytic converters for purifying (by reduction/oxidation) exhaust gases, containing high concentrations of NO x , CO, SO 3 , hydrocarbons and others [3,4].…”