Corrosion inhibitor

A preparatory coating applied to a substrate before an adhesive, sealant, coating or waterproofing membrane, improving adhesion by sealing porosity, binding dust or providing a chemically compatible surface. Primer selection depends on both the substrate and the product to be applied over it.

The formation of a thin, stable oxide film on a metal surface that markedly reduces its chemical reactivity, occurring naturally on metals such as stainless steel and aluminium or induced deliberately by chemical treatment. Passivation treatments for stainless steel remove free iron contamination and restore the protective chromium rich oxide layer.

A primer containing a high loading of metallic zinc dust in an organic binder, usually epoxy, or an inorganic silicate binder, providing galvanic protection to steel in a similar way to galvanising. It requires a high standard of blast cleaned surface so that the zinc makes electrical contact with the steel.

A coating that protects primarily by impermeability, isolating the substrate from water, oxygen and dissolved ions rather than by galvanic or inhibitive action. High build epoxies and coatings pigmented with lamellar materials such as micaceous iron oxide or glass flake are typical examples.