Comparative study of tarnishing resistance of several coloured gold based alloys.

<title/> The stability of coloured gold alloys may be dependent on the environment that involves them. This paper is concerned with the effect of an artificial sweat solution in the stability of several gold base alloys with different colours. The changes in the samples physical properties, namely in colour, brightness and reflectance, were measured for several periods of immersion. In the end of the tests, the samples surface were analysed by optical and SEM/EDS microscopy. Two types of alloys (purple and blue coloured alloys) showed to be sensitive to the artificial sweat solution. The other tested alloys have a high resistance to tarnishing when compared to the results obtained for pure gold. [ABSTRACT FROM AUTHOR]