An electrochemical impedance study of the corrosion of Tytin dental amalgam was carried out in electrolytes similar to artificial saliva with or without lactic acid, and in standard inorganic artificial saliva with higher ionic concentration. Spectra were recorded in the presence and absence of dissolved oxygen to show the importance of the formation of oxide film and the adsorption of the organic component, as well as the exposed surface microstructure. The data, supported by open circuit potential and polarisation curve experiments, obtained in the presence and absence of dissolved oxygen are interpreted in the light of possible corrosion mechanisms. (C) 2004 Elsevier B.V. All rights reserved.