A model for the dehydration of waterborne basecoat

In vehicle manufacturing, a common topcoat process sequence is the application of a waterborne basecoat, partial dehydration, application of a solventborne clearcoat, then curing at approximately 150°C. Anecdotal evidence suggests that under “harsh” (high temperature and velocity) dehydration conditions, a skin can be formed, which can trap excess water in the basecoat. Upon curing, the excess water forms vapor that can burst through the topcoat, leading to surface imperfections, termed pinholes or pops.