Protein adsorption on stainless steel in aqueous solution: An EIS, XPS, and IRRAS study

The adsorption of Bovine Serum Albumin (BSA), and its influence on the electrochemical behaviour in deaerated 0.05M H ₂SO ₄ solution of a ferritic stainless steel, Fe-17Cr, was studied by electrochemical methods (time dependence of the corrosion potential E _cor, polarization curves, EIS) and surface analysis techniques (PM-IRRAS, XPS). The electrochemical measurements show a corrosion inhibition by the BSA at E _cor. The charge transfer resistance decreases and hence the corrosion current of the alloy increases with immersion time at E _cor, but this phenomenon is much less marked in the presence of BSA. The LF response of the impedance diagrams plotted at E _cor and its evolution with immersion time is modified by the presence of the BSA, which suggests that the protein is directly or indirectly involved in the electrochemical processes at E _cor. Impedance measurements performed after passivation of the alloy at 0 V vs. 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 the BSA is present on the surface at both E _cor and 0 V. From the detailed analysis of the C 1s XPS region, it can be concluded that the BSA molecules adsorbed on the surface at both potentials are chemically intact. The amount of adsorbed BSA is quite similar at E _cor and 0 V. 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.