Adhesive strength of powder coated aluminium substrates

Adhesive strengths of differently pretreated powder coated aluminium substrates were evaluated using the pull-off and the tape tests in the dry and wet conditions. Various accelerated test chambers were employed to evaluate the corrosion behaviour of the samples. Scanning electron microscopy (SEM), with energy dispersive X-ray analysis (EDX) were also employed to the better understanding of the nature and morphology of the differently pretreated aluminium substrates prior to and after the accelerated tests. rated tests and wet adhesion measurements showed that the degreased samples demonstrated a better performance than Polyacrylic acid (PAA) treated samples. The chromate/phosphate conversion coating (CPCC) treated samples gave the best performance and the Polyacrylic acid/ hexafluorozirconic acid treated samples (PZr) gave marginally second best performance in anti-corrosive behaviour. on the results obtained from the different experiments, it is argued that these studies may provide sufficient evidence to show that hydrolysis may destroy interface bonds between PAA and aluminium substrate. Moreover, SEM/EDX analysis, suggest that, the thin PAA polymeric layer was replaced by a crystalline, thick hydrated oxide layer, when samples were exposed to humid conditions.