Corrosivity category

An accelerated laboratory corrosion test in which coated or plated specimens are exposed to a fine fog of salt solution in a closed chamber under standardised conditions, as described in ISO 9227 and ASTM B117. Results are used for comparative and quality control purposes, as correlation with service life in real atmospheres is limited.

The gradual change in the appearance and properties of a material caused by outdoor exposure to ultraviolet radiation, moisture, temperature cycling and airborne pollutants. Coating and material durability is assessed by natural exposure trials and by accelerated weathering tests in the laboratory.

A layer of material applied to a substrate to protect it, decorate it or give it specific functional properties. In protective applications the coating is the main barrier against corrosion, weathering, chemical attack and abrasion, and is usually built up as a system of primer, intermediate and finish coats.

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.