Novel approach to measure water vapor permeability in pre-painted metals using adapted cup method: Correlation between permeation rate and tendency to blistering

Abstract

Corrosion protection ability of paint systems is influenced by the amount of water transported to the metal/paint interface through defects in organic coatings. It can be precisely determined using the blind hole cup method with a free-standing paint film. In this paper, a procedure for preparation of free-standing paint films from as-received prepainted metal sheets is described. The blind hole cup method was able to provide accurate information about water actually permeating to the metal/paint interface excluding the water present in blind defects. The paint system with a lower water permeability was less blistered after both accelerated test and field exposure.