The corrosion resistance of Wiron^®88 in the presence of S. mutans and S. sobrinus bacteria

The corrosion resistance of Wiron^®88, a Ni–Cr–Mo alloy, was evaluated in liquid growth media in the absence and presence of the Streptococcussobrinus and Streptococcus mutans strains. Open circuit potential measurements, cyclic voltammetry, linear sweep voltammetry, as well as electronic microscopy coupled to electron diffraction spectroscopy (SEM/EDS), were the main techniques used in this study. It was concluded that the presence of S. sobrinus and S. mutans have only a slight effect on the corrosion resistance of the Wiron^®88 alloy, with the S. mutans being slightly more aggressive. For both strains the corrosion resistance R_p is of the same order (kΩ cm²). After 24 h immersion the S. sobrinus lead to and R_p of 11.02, while the S. mutans lead to of 5.59 kΩ cm². SEM/EDS studies on the Wiron^®88 samples, with 24 days of immersion, at 37 °C, have confirmed bio-corrosion of the alloy occurring through the dissolution of Ni as Ni²⁺ and formation of chromium and molybdenum oxides. The bacterial adhesion to the surface is not uniform.