Optimized nanoporous alumina coating on AA3003-H14 aluminum alloy with enhanced tribo-corrosion performance in palm oil

This study aimed to prepare nanoporous anodic alumina on AA30031-H14 aluminum alloy using a mild anodization process with minimal working voltage and treatment time. The microstructural features, mechanical properties, and tribocorrosion behavior of the coatings were assessed to determine the optimum conditions for the fabrication of nanoporous anodic alumina on AA3003-H14 alloy. The microstructural analysis showed both uniform and nonuniform pore nucleations during anodization in H2SO4/C2H2O4, H2SO4/H2CrO4, and EG/H2O/NH4F electrolytes, where the optimal nanoporous structure with an average thickness, porosity, pore diameter, and interpore distance of 382 nm, 19%, 16 nm, and 35 nm, respectively, was developed after a short-time mild anodization for 30 min at constant potential of 12 V using 15 wt% H2SO4 electrolyte. The XRD profiles indicated formation of a highly-disordered and amorphous nanoporous anodic alumina. Due to the loss of mechanical properties after heat treatment at 450 degrees C for 90 min, Vickers microhardness of the samples decreased drastically from 124 to 90.5 HV, respectively. The wear analysis indicated an improved tribological behavior by mild electrochemical anodization owing to the development of nanoporous anodic alumina, which acted as the liquid lubricant reservoir and increased the tribological performance of the workpiece. In addition, the heat treated specimen showed the lowest corrosion rate of 0.079 mm.y(-1) and utmost corrosion protection efficiency of 95.24% following exposure in palm oil methyl ester (B100). This novel nanoporous configuration not only endows excellent tribological performance in the biofuel combustion environment, but also particularly decreases consumption of liquid lubricants through a facilitated multiphase lubrication mechanism.