BSA adsorption on Fe-17Cr in acid solution: Electrochemical behaviour and surface composition

This chapter presents a study in which the electrochemical behavior and the surface composition of a Fe-17Cr stainless steel in deaerated 0.05M H₂SO₄ solution was studied as a function of potential and Bovine Serum Albumin (BSA) concentration. The Electrochemical Impedance Spectroscopy (EIS) measurements reveal a corrosion inhibition by the BSA at the corrosion potential Ecor and show that the presence of the protein has no effect on the electrochemical behavior of the alloy polarized in the passive domain. The XPS analyses demonstrate that the adsorption of BSA takes place on the Fe-17Cr surface both at Ecor and in the passive region, and that the adsorbed BSAmolecules are chemically intact. From a 3-layer model, the thickness of the protein layer is estimated to about 4 nm, irrespective of the BSA concentration and the potential, which would correspond to 1 or 2 monolayers. The XPS analyses also show that BSA has no effect on the chemical composition of the mixed Fe₂O₃-Cr₂O₃ oxide layer both at Ecor and in the passive region. Thus, the corrosion inhibition effect evident at Ecor by EIS occurs due to the protein and not to a change in the chemical composition of the oxide layer.