By immersion tests and potentiodynamic electrochemistry corrosion behaviour of WC-Co,Ni based cemented carbides in 1N sulphuric acid and in an artificial dielectric (1 g/l KCl) has been investigated. Magnetic saturation (by adjustment of a carbon deficit, low - high), Nickel content of the binder (0 - 2 %) and amounts of chromium carbide (0 - 1 %) and molybdenum carbide additions (0 0,7 %) have been varied. By TEM investigations with high resolution EDS analysis the chemical composition of the binder has been determined. Most important parameter is magnetic saturation. The lower it is, the higher is the amount of dissolved tungsten in the binder and the higher is the corrosion resistance in acids. In neutrale solutions tungsten yields to an increased corrosion rate due to tungstate formation. Nickel generally improves corrosion resistance as well as dissolved chromium in the binder. Molybdenum has the same effect like tungsten, however investigated concentrations were too small to get large influences on corrosion behaviour.