Improvement in corrosion resistance of micro‐arc oxidation coating on PVD Ti‐coated aluminum alloy 7075

Abstract

Surface treatments are always needed to enhance corrosion-resistant performance of aluminum (Al) alloys when they are used in seawater environments. The paper aimed to prepare the composite oxide ceramic coating on Al alloy 7075 by combining micro-arc oxidation (MAO) and magnetron sputtering technology. The Al substrate was precoated with titanium (Ti) layer by using the magnetron sputtering technology and then treated by MAO in the alkaline aluminate electrolyte, resulting in a composite MAO coating, which is composed of Al 2 O 3 and TiO 2 along with the complex oxide (Al 2 TiO 5 ). The potentiodynamic polarization and electrochemical impedance spectroscopy were carried out to evaluate the corrosion performance of the MAO coatings in 3.5 wt% NaCl solution. Better corrosion resistance was observed for composite oxide coating than the reference MAO coating on the bare Al, as evidenced by the higher corrosion potential of −0.664 V versus Ag/AgCl and the lower corrosion current density of 4.41 × 10 -6 A/cm 2 .

Effects of Er2(SO4)3 doping on characteristics of MAO coating

“…24,25 Ti 4+ produced from the matrix reacted with OH − to generate anatase TiO 2 . Meanwhile, a tiny amount of Al element formed γ-Al 2 O 3 by oxidation and then interacted with TiO 2 to produce Al 2 TiO 5 26 under the influence of an alkaline electrolyte. The absence of Er 2 (SO 4 ) 3 in the XRD picture was caused by the coating's low Er content, which did not reach the minimum content that can be detected by XRD.…”

Effect of annealing on AZ31 magnesium alloy on MAO coatings

“…The MAO process is a method of coating a ceramic surface on an alloy, which effectively improves its corrosion resistance. [9][10][11][12] In previous experiments on MAO, researchers have considered various factors, such as electrolyte composition, electrical parameters and additives. However, there are few literature reports on how deformation and annealing can also affect the corrosion behaviour of MAO coatings on alloy matrices.…”