The purpose of this study was to fabricate black ceramic coatings on 7050 aluminum alloy via micro-arc oxidation (MAO) at durations of 10, 15, 20 and 25 min. Results demonstrated that extended oxidation time (10–25 min) progressively enhanced coating thickness and surface roughness while reducing porosity and structural defects, thereby improving mechanical strength and durability. Among all tested durations, the 20-min MAO coating exhibited optimal performance, achieving the highest hardness (180 HV), lowest porosity (2.584%) and minimal corrosion current density (Icorr = 1.214 × 10−7A/cm2) in 3.5% NaCl solution. Long-term immersion tests confirmed superior corrosion resistance for coatings within this optimized time range.
The MAO treatment was performed on 7050 aluminum alloy using a JHMAO-380/20H MAO instrument in a silicate and phosphate electrolyte system with NH4VO3 as a coloring agent. Four different oxidation times were set to prepare the coatings. The microstructure, hardness, tribological properties and corrosion resistance of the coatings were tested and analyzed.
At a micro-arc oxidation time of 20 min, the black coating exhibits minimal microcracks and local defects, the lowest porosity, and optimal corrosion resistance, with concurrent peak Vickers hardness (181HV). However,prolonged MAO time increases coating thickness at the expense of reduced corrosion resistence.
This study systematically analyzes the impact of oxidation time on the properties of black MAO coatings and determines the optimal oxidation time, providing significant insights for the application of MAO technology in the surface treatment of aluminum alloys.
