Influence of bovine serum albumin in sulphuric acid aqueous solution on the corrosion and the passivation of an iron–chromium alloy

The adsorption of bovine serum albumin (BSA), and its influence on the electrochemical behaviour in deaerated 0.05 M H2SO4 solution of a ferritic stainless steel, Fe–17Cr, was studied by electrochemical methods (time dependence of the corrosion potential Ecor, polarization curves, EIS) and surface analysis techniques (PM-IRRAS, XPS). The electrochemical measurements show a corrosion inhibition by the BSA at Ecor. The charge transfer resistance decreases and hence the corrosion current of the alloy increases with immersion time at Ecor, but this phenomenon is much less marked in the presence of BSA. Impedance measurements performed after passivation of the alloy at 0 V versus SSE show that the presence of protein has no effect on the electrochemical behaviour of the passivated alloy surface. Surface analysis of the stainless steel samples by PM-IRRAS and XPS shows that chemically intact BSA molecules are adsorbed on the surface at Ecor and 0 V. The amount of adsorbed BSA is quite similar at both potentials. All these results demonstrate that the adsorption of BSA takes place on the Fe–17Cr surface both at the corrosion potential and in the passive region, and the BSA has a corrosion inhibition effect when the surface is not fully passivated.