The present study aims to compare the corrosion and tribocorrosion behaviour of nitrocarburized, gas-nitrided, fluidized-bed nitrided, and plasma-nitrided Impax Supreme (equivalent to AISI P20) pre-hardened plastic mould steel. Corrosion behaviour was investigated by electrochemical impedance spectroscopy and potentiodynamic polarization in 3.5 wt% NaCl solution. Tribocorrosion tests were performed in the same solution under open circuit potential during sliding against 10 mm alumina balls. Results showed that plasma-nitrided samples presented better corrosion behaviour in terms of tendency to corrosion, corrosion rate, and polarization resistance, as compared to the other studied surface treatments. Together with nitrocarburised samples, plasmanitrided samples also exhibited lower tendency to corrosion under sliding.