Observations on Galvanic Corrosion Induced Paint Adhesion Loss

The locus of failure occurring with corrosion induced paint adhesion loss on the steel surface of one side galvanized sheet has been investigated using the scanning electron microscope. Controlled laboratory experiments to simulate alkaline attack of phosphate crystals in the conversion coating and bulk alkyd primer saponification have been used to provide a basis for interpreting the features observed on salt spray test panels, and on the back side of paint stripped after adhesion loss. The controlling failure mechanism is shown to be attack along primer-steel interfaces.