Effect of Micro-Arc Oxidation Voltage on the Surface Morphology and Properties of Ceramic Coatings on 7075 Aluminum Alloy
Satbayeva Z. Zhassulan A. Rakhadilov B. Shynarbek A. Ormanbekov K. Leonidova A.
July 2025Multidisciplinary Digital Publishing Institute (MDPI)
Metals
2025#15Issue 7
Ceramic oxide coatings were fabricated on 7075 aluminum alloy via micro-arc oxidation (MAO) in a silicate-phosphate electrolyte under voltages of 250 V, 300 V, and 350 V for 600 s. The effect of the applied voltage on the surface morphology, microstructure, phase composition, microhardness, roughness, coating thickness, and corrosion resistance was systematically studied. The coating obtained at 300 V demonstrated a dense structure with relatively low surface roughness (2.3 μm) and a thickness of approximately 70 μm. This sample also exhibited the most balanced performance, combining relatively high microhardness (~422 HV) and the lowest corrosion current density (6.1 × 10−7 A/cm2) in a 3.5 wt.% NaCl solution. X-ray diffraction patterns revealed the presence of both γ- and α-Al2O3 phases in all coated samples, with a relative increase in α-phase intensity observed at an intermediate voltage. The results demonstrate that the applied voltage plays a critical role in determining the coating structure and performance, offering insights into the surface treatment of high-strength aluminum alloys for engineering applications.
7075 Al alloy , ceramic coating , corrosion resistance , micro-arc oxidation , silicate-phosphate electrolyte , surface morphology
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