Study on Preparation, Microstructure and Properties of Micro-Arc Oxidation Ceramic Coating on AZ91 Magnesium Alloy in Phosphate Electrolyte

Abstract

The micro-arc oxidation behavior of AZ91 magnesium alloy in alkaline phosphate electrolyte was studied. The effect of phosphate on the microstructure and properties of micro-arc oxide film was investigated and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectrum (EDS) and salt spray test. The results show that phosphate concentration has an important effect on the surface morphology, phase structure, thickness and corrosion resistance of micro-arc oxidation film. With the increase of phosphate concentration from 5g/L to 30g/L, the film quality decreases, the surface roughness increases, the thickness decreases and the corrosion resistance decreases. So in phosphate electrolysis the lower phosphate concentration in the liquid system is helpful to the formation of better film quality.

Analysis of technological approaches to electrochemical surface treatment of aluminum alloys

“…On the surface there are crater-like melted depressions formed during the burning of spark and microarc discharges. Such depressions are probably the outer part of the burning channel -closed (dead-end) pore [43]. Taking into account the curvature radius of the probe, it can be found that the size of such pores varies from several tens of nanometers to micrometers and more and increases in the series of alloys A99<D16<AL25.…”