The influence of reduced pressures on the film formation of cathodic electrodeposition paints

•The appearance of electrodeposition coatings shows clear pressure dependence.•Reduced pressure gives textured films, further decrease leads to smoother films again.•Film thickness and charge flow are pressure dependent as well.•The effects can be explained by adhesion and detachment of hydrogen bubbles.•The proposed model concept is supported by electrical data. Within the last decades, cathodic electrodeposition paints have experienced extensive economic success – most prominently in automobile body coating. However, to date, it is not possible to calculate the deposition behaviour of cathodic electrodeposition coating materials exclusively from bath and application data, since the key mechanisms responsible for the film formation are not sufficiently understood. By performing coating experiments with cathodic electrodeposition paints at reduced pressures, in this work, experimental evidence for a pressure dependent procedure of film formation is given. Supported by charge-flow and current-time plots, this fact is attributed to the influence of the pressure-dependent volumes of the generated hydrogen bubbles, thus providing new insights into the deposition behaviour of cathodic electrodeposition paints.