Bake oven induced variation of surface chemistry on electrocoat paint: Effect on primer-electrocoat intercoat adhesion

The interplay of bake oven processing environment and surface/interfacial chemistry, and their effect on intercoat adhesion has been investigated for a model primer/electrocoat paint system. X-ray photoelectron spectroscopy (XPS) surface analysis established that a prominent ether component in the C 1s core level spectrum correlated with a polyether-based crater-control additive in the electrocoat that surface-segregates during cure. Laboratory-simulated bake oven experiments confirmed that better adhesion characteristics were realized by removal of this electrocoat overlayer through reaction with nitrogen oxides and high levels of moisture present in the cure environment of production direct-fired ovens. Details of the effect of bake oven atmosphere on cure chemistry for direct- versus indirect-fired ovens are presented.