Tribological mechanism of micro-arc oxidation coatings prepared by different electrolyte systems in artificial seawater

The micro-arc oxidation (MAO) coatings were prepared in four different electrolyte systems, including mixed acid, phosphate, phosphate-aluminate and phosphate-silicate electrolytes. The friction and wear properties of MAO coatings in ambient air, seawater and four groups of saline solutions related to seawater were investigated. The results showed that the addition of silicate to phosphate could increase the density of the coating. The phosphate-aluminate ceramic layer exhibited the lowest wear rate in various environments. Additionally, the friction coefficient and wear rate of MAO coating in seawater were lower than those in ambient air, which was due to the boundary lubrication effect of seawater. Meanwhile, the presence of divalent metal salts in seawater made its lubricity better than other salt solutions.

Automated summary

Adding silicate can increase the density of the coating, and phosphate-aluminate ceramic layer exhibits the lowest wear rate in various environments. The friction coefficient and wear rate of MAO coating in seawater are lower than those in ambient air due to the boundary lubrication effect of seawater, with the presence of divalent metal salts making seawater more lubricous than other salt solutions.