Corrosion behavior and adhesion strength of PEO/Epoxy duplex coating applied on aluminum alloy

Purpose This paper aims to increase protection behavior of epoxy coating on aluminum alloys with plasma electrolitic oxidation (PEO) process as pretreatment and to investigate the corrosion properties of duplex coating system on aluminum alloy. Design/methodology/approach The study used micro structure study, electrochemical impedance spectroscopy (EIS) investigation, water uptake investigation and pull-off test. Findings This study was done to investigate the effect of urea as an additive, which alters the current density and time of process parameters in the protective performance of epoxy coating on the aluminum substrate. The protective behavior of double-layer coatings was examined using EIS in 3.5 per cent NaCl solution. In addition, the adhesion strength of double-layer coatings was evaluated using pull-off test, and the results demonstrated that the adhesion strength of sample with higher content of urea and current density is about two times that of sample without PEO preparation. Originality/value The protective properties and adhesion strength of epoxy coating can be increased with PEO pretreatment.