The effect of the saliva formulation on brass corrosion

The composition of natural saliva is strongly variable and unstable outside the oral cavity, therefore corrosion tests are usually performed in artificial saliva solutions. In this study the effect of the composition of various saliva solutions on the corrosion behavior of a CuZn37 alloy, exposed for 1, 3, and 16 h to the solutions, is investigated by using electrochemical measurements, optical microscopy, and X-ray photoelectron spectroscopy (XPS). The solutions investigated in this study are: Darvell, Carter-Brugirard, and SALMO, selected for their composition that mainly differs in the organic compounds' content. Electrochemical measurements show that the open circuit potential and the polarization resistance increase with exposure time in the solutions, indicating a decrease in the corrosion rate. The corrosion rate (mu m/year) in the Darvell solution is found to be two times higher than the other artificial saliva formulations and varies in the order: Darvell > Carter-Brugirard > SALMO. These data suggest that the presence of different organic compounds might limit the formation of a stable protective surface film as confirmed by XPS surface analyses.