Corrosion behaviour of austenitic stainless steels in phosphate buffer saline solution: synergistic effects of protein concentration, time and nitrogen

Proteins and their concentrations have immense influences on the corrosion of metallic implants. This work systemically investigated the effects of bovine serum albumin (BSA) with time on the corrosion behaviour of austenitic stainless steels (SSs) in phosphate buffer saline (PBS) solution. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning Kelvin probe (SKP) experiments were conducted to study the interactions of BSA and the passive layers and to measure the corrosion parameters. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to determine the chemical compositions and surface morphologies. It was observed that the presence of BSA had a significant inhibition effect on the corrosion behaviour of SSs and on improvement of the corrosion resistance with BSA concentrations up to 2.0 g L-1. The SKP results demonstrated that after immersion in PBS solution with BSA, the surface potential difference and the electrochemical non-homogeneity of SS decreased. Surface analysis with XPS and AFM established that corrosion resistance may be related to favorable adsorption of BSA on the steel surface. However, at very high concentrations and with higher immersion times, BSA chelated with the corrosion products, causing disruption of the protective film; thus, it accelerated the corrosion of the alloy. These results allowed the determination of a corrosion mechanism in the presence of protein. It was also established that a low concentration of BSA has significant effects on the corrosion resistance of nitrogen-containing steel with long term exposure.