Stone-chipping and adhesion deterioration of automotive coating systems caused by outdoor weathering of underneath layers

• The ED-coated panels were exposed to natural weathering condition for various times.
• The weathered samples were then coated with primer and topcoat layers.
• The chemistry and morphology of the weathered ED layer were studied.
• ED layer had a very low resistance against weathering degradation.
• Underneath layer weathering had a deleterious effect on the chipping and adhesion.

The main objective of this study is to investigate how the weathering of underneath electro deposition (ED) layer affects the overall stone-chipping behavior of an automotive coating system. The ED-coated panels were exposed to natural weathering condition before being further coated with top layers. It was found that the underneath layer weathering has a deleterious effect on the chipping and adhesion of the whole coating system. The chemistry and morphology of the weathered ED layer demonstrated that the chalky-like ED surface could not provide a desired foundation for top layers, leading to a coating structure collapse.

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