What causes adhesion failure on metal?

Adhesion failure on metal substrates, resulting in blistering, flaking/delamination and corrosion, is usually due either to surface contamination or poor surface preparation. Among the most common types of surface contamination are grease on new galvanised surfaces and wax residue resulting from the use of chemical paint strippers, which should be cleaned with an emulsifying Oil and Grease Remover. Dust and general debris should always be vacuumed away before painting. In terms of surface preparation, the failure to remove millscale from hot rolled mild steel prior to painting can lead to serious problems months or even years later. Similarly, painting over rust can result in the paint film flaking or the rust breaking through the paint film.