Formation of a semiconductive surface film on nanomultilayered TiN/CrN coatings and its correlation with corrosion protection of steel

Corrosion resistance of nanomultilayered TiN/CrN coatings has been evaluated in saline aqueous neutral solution and compared with monolayered TiN and CrN references. Coatings have been deposited by magnetron sputtering on M2 tool steel, as well as on glass strip, to determine their intrinsic electrochemical behavior. Corrosion resistance afforded by CrN is better than TiN, which is explained by the formation of a thin oxide passive film with favorable semiconductive properties. Nanostratified structure improves the coating density, but the electrochemical behavior is however mainly controlled by the nature of the outer layer, which must be CrN to optimize protection ability.