Hydration-dehydration behavior induced densification of porous plasma electrolysis coating

Abstract Control of porosity in plasma electrolysis (PE) coating is extremely important for a wide set of applications. Up to this study, utilizing the phase transformation reactions between γ-alumina (γ-Al 2 O 3 ) and boehmite (AlOOH) to densificate the porous surface of the coating deposited on Al-Mg-Si alloy has been rarely reported. For this aim, the PE coating sealed by boiling water is subjected additionally to an annealing treatment at 633 K for 30 min. The annealing treatment not only decreased the average size of micropores and the degree of porosity in the coating but also promoted the formation of γ-Al 2 O 3 through the dehydration reaction of AlOOH which was formed during the sealing treatment of PE coating by the boiling water. Accordingly, the corrosion resistance of the annealed sample was superior to other cases.