This article deals with corrosion resistance comparison of plasma nitrided 42CrMo4 steel to another surface technologies used for breech mechanism manufacturing in the armament production. Increasing of demands on materials used for armament production and in other industrial applications leads to the innovation of technologies in the field of surface treatment, especially wear resistance, surface hardness, running-in properties and corrosion resistance, optical demands and others. For the evaluation of experimental corrosion resistance were plasma nitrided samples of 42CrMo4 steel compared with alkali blackening, manganese phosphate and Arcor technologies. The conditions of plasma nitriding process were set to provide exactly defined nitride layers with defined parameters. In this case, the above-mentioned surface technologies were applied to individual samples of 42CrMo4 steel, which were subsequently metallographically evaluated and the hardness and microhardness were measured. The corrosion resistance comparison was realized by the NSS corrosion tests in the condensation chamber and visually evaluated. The results and comparison of corrosion resistance of plasma nitrided steel samples with above-mentioned surface treatment technologies showed significant differences in corrosion rate propagation. Thank to different plasma nitriding conditions, there are evident differences in corrosion resistance between the plasma nitrided steel samples as well. The corrosion resistance evaluation is supplemented by the surface layer characteristics. K e y w o r d s : plasma nitriding, breech mechanism, corrosion resistance