Passive materials are materials that, due to their chemical composition and structure, form a natural protective layer on their surface. This protective layer, also called a passivation layer, protects the material from corrosion and other types of chemical or electrochemical degradation.

Passive materials include anodic coatings, aluminum (with low copper content), ceramics, chromate layers, glass, high alloy steel, nickel, oxide layers, plastics, silver, stainless steel, tin and zinc.

In adhesive technology, passive materials require activators because their surface properties influence the reaction speed of the adhesive, which results in slower curing.