Correlation between Microstructural Properties and Electric Parameters of Micro-Arc Oxidation Coatings on 5052 Aluminum Alloys with Improving Wear and Corrosion Resistance

Abstract

Aluminum (Al) alloys are lightweight and machinable and have been widely used in industrial applications, particularly the formation of complex mechanical parts. However, the 5052 Al alloy frequently encounters problems like corrosion and wear during its service life, significantly impacting the equipment’s longevity. This study investigated the effects of pulse voltage (320 to 400 V) and frequency (50 to 200 Hz) on the growth and surface morphology of 5052 Al alloy films formed through micro-arc oxidation (MAO) to improve their corrosion and wear resistance while maintaining a surface roughness of less than 1 μm. The results indicate that higher operating voltages and frequencies correlated with increased thickness in the resulting ceramic oxide films formed using MAO. In addition, as the pulse frequency increased, the distribution of the holes became more uniform across the surface. We examined the surface and cross-sectional morphology, as well as the thickness of the MAO coatings, through scanning electron microscopy (SEM). The corrosion and wear resistance of the MAO coatings formed under different electrical parameters were analyzed using electrochemical corrosion tests and scratch tests. The MAO coatings produced at 400 V and 200 Hz were the thickest, at approximately 4.8 μm, and demonstrated superior corrosion and wear resistance. These coatings demonstrate significantly reduced wear width, highlighting their exceptional resistance to corrosion and wear. Hole cracking occurred only above the top layer of the coating and not beneath the mid-layer, which protected the substrate from damage due to the direct passage of Cl ions through the holes.