Organic Protective and Decorative Coatings for Metal Containers

The adhesion of paint to metal is affected by the nature and condition of the metal surface at least as much as by the nature of the paint. Paints of all types appear to adhere well to most very clean metals but the adhesion of some paints is sensitive to extremely low levels of contamination—for example, by stearic acid. Non-polar hydrocarbon contaminants do not reduce adhesion seriously unless they are present in amounts sufficient to weaken the cohesion of an interfacial layer. The surfaces of almost all commercial metal sheets are contaminated and require pretreatment before painting. The nature of the contaminants present are discussed and laboratory techniques for obtaining cleaning surfaces are reviewed.