Numerical analysis of surface-tension-driven coating flow

Bondline readout (BLRO) is a coating defect frequently exhibited on adhesively bonded, polymeric automotive body panels painted with high‐glamour/flow clearcoats. BLRO or telegraphing results from Marangoni‐type, surface‐tension‐driven flows. The goal of this study is to use an efficient one‐dimensional numerical code (based on the lubrication approximation) to obtain further insight into the mechanism of temperature‐ and concentration‐induced BLRO flows in order to validate a proposed BRLO mechanism and ultimately to help eliminate the highly undesirable BLRO coating defect. Further insight is realized by investigating numerically the effects on BLRO of gravity and five parameters—initial film thickness, heating rate, viscosity, solvent volatility, and solvent‐to‐resin surface‐tension ratio. Possible solutions to the BLRO problem are discussed.