Zinc rich coatings have long been used in the protective coatings industry as one of the primary means of steel substrate protection against corrosion. The primary protection mechanism has historically been galvanic sacrificial loss of zinc metal and the simultaneous formation of protective zinc oxides and salts. Various standards and customer specifications exist to ensure that the coating will provide the necessary corrosion protection for the life of the asset.
Zinc-rich primers, with zinc dust loadings of 80-85% by weight in the dry film, are often the preferred primer during new construction of assets placed in environments with high atmospheric corrosivity. Coating standards such as SSPC-Paint 20 and ISO 12944 demand that zinc-rich primers contain at least 65% and 80% zinc dust by weight in the final dry film, respectively. Traditional zinc rich primers need this high zinc loading to achieve galvanic protection of steel. New technology allows us to develop zinc primers with a lower content of zinc and/or different zinc morphology than dust to provide similar or better corrosion protection to the steel.
The role of a Coating Inspector has evolved considerably over the past few decades, and the responsibilities have increased over what used to be a rather straightforward job: to verify that surface preparation and coating application meet the project specification requirements. Today there are week-long or multi-week basic and advanced coating inspection courses, specialty courses that are industry-specific (e.g., bridge, nuclear), courses that are substrate-specific (e.g., concrete coatings inspection) and even coating-specific (e.g., inspection of thermal spray coatings).