Preparation and Corrosion Behavior in Marine Environment of MAO Coatings on Magnesium Alloy

Abstract

To improve the corrosion performance of magnesium alloys in the marine environment, the MAO, MAO–Cu2CO3(OH)2·H2O and MAO–Cu2P2O7 ceramic coatings were deposited on AZ91D magnesium alloys in basic electrolyte and the discoloration mechanism of the Cu-doped MAO coatings and the corrosion behavior of the three MAO coatings in the artificial seawater solution were investigated by SEM, EDS and XPS. The results indicated that the formation and discoloration mechanism of the brown MAO ceramic coatings were attributable to the formation of Cu2O in the coatings. Though the three MAO coatings had a certain protective effect against the corrosion of AZ91D substrate in the artificial seawater, the distinctive stratification phenomenon was found on the MAO–Cu2P2O7 coated sample and the corrosion model of the MAO–Cu2P2O7 coatings in the immersion experiment was established. Therefore, the brown Cu-doped MAO coatings were speculated to significantly reduce the risk of the magnesium parts in marine environments.

Corrosion and Wear Behavior of TiO2/TiN Duplex Coatings on Titanium by Plasma Electrolytic Oxidation and Gas Nitriding

“…When a capacitor is omitted from the circuit, no current can flow because, when the capacitor is charged, the current will not pass, and the circuit will be cut off. The dense oxide layer on the surface of the titanium also has this effect and, such as a capacitor after being fully charge, disrupts the electrical circuit by reducing the corrosion rate [ 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 ]. Based on the EIS diagrams and the obtained data, it can be concluded that the corrosion resistance of the sample with plasma electrolytic oxidation coating is better than that of the uncoated sample.…”

Effect of (NH4)2ZrF6, Voltage and Treating Time on Corrosion Resistance of Micro-Arc Oxidation Coatings Applied on ZK61M Magnesium Alloys

“…This can also be proved in Lee’s research [ 32 ], which clarified that the incorporation of ZrO 2 can improved corrosion property of MAO coatings effectively. It should be noted that there exist lots of MgF 2 concentrated in the micropores, according to Liu’s research [ 33 ], the deterioration rate of the MAO coating compounds can be reduced by the presence of MgF 2 when MAO coating was exposed to corrosive medium, so the existence of MgF 2 is of great help in preventing corrosive ions from reaching substrate surface quickly [ 34 ]. In addition, this is also the result of compacter structures and thicker coatings working together.…”

Influence of Surfactants on Microstructure and Properties of MAO Coated on Aluminum Alloy in Marine Construction

“…With the development of science and technology, aluminum alloys have been developed rapidly, especially in the application of marine construction [1][2]. Aluminum alloys are light in weight and possess many outstanding mechanical properties.…”