The effect of the saliva composition 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 work the effect of the composition of various saliva solutions on the corrosion behaviour of a CuZn37 alloy, exposed for 1, 3 and 16 hours to the solutions, is investigated by using electrochemical measurements, optical microscopy and X-Ray Photoelectron Spectroscopy. The solutions investigated in this work are: Darvell (D), Carter-Brugirard (C-B) and SALMO, selected for their composition that mainly differs in the organic compounds content. Electrochemical measurements show that the open circuit potential (OCP) and the polarization resistance Rp increase with exposure time in the solutions, indicating a decrease in the corrosion rate. The corrosion rate (µm/year) in the Darvell solution is found to be two times higher than the other artificial saliva solutions 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.