Tribological effects of pores on an anodized Al alloy surface as lubricant reservoir

Porous anodic alumina (PAA) templates having three kinds of nanometer pores were manufactured to investigate the effects of pores on an anodized aluminum surface as lubricant reservoir. Ball-on-disk wear tests of the PAA templates were carried out in the three types of lubrication conditions. The PAA templates submerged under water for 30 min showed lower friction coefficient and longer transition time to steady state compared to those that were not submerged. Pores act as a lubricant reservoir because the water stored inside the pore is released to the surface due to elastic–plastic deformation. However, the effect of oxide layer developed by tribochemical reaction on the surface is greater than lubricant reservoir effect of the pore. In particular, the submerged PAA templates with 260 nm pores under dry lubricant condition formed more hydroxide layers than other cases, which resulted in the decrease in friction.