The effects of seven different additives including ethanol, methanol, glycerin, triethanolamine (TEA), urea, formamide and sodium dodecyl sulfate (SDS) were investigated on the incorporation of alumina nanoparticles (NPs) and submicron particles in plasma electrolytic oxidation of AZ31B magnesium alloy substrates. Initial results from weight changes indicate that the additives did not improve the incorporation of submicron particles, whereas the incorporation of NPs was indeed enhanced. The most efficient additive was found to be urea which resulted in the highest content of alumina NPs to be incorporated. Later, the impact of urea concentration was investigated and it was discovered that the highest incorporation of NPs occurred at 20 g/l of urea concentration, in which NPs were properly dispersed into the solution and their size was decreased. Corrosion and wear properties of films which were evaluated either with or without urea were studied. The highest content of incorporated alumina NPs was obtained at 20 g/l of urea. DLS results show that 20 g/l urea caused the lowest size of particles in the electrolyte. The highest corrosion resistance (with a current density of 1.5 mA/cm2) and the lowest wear rate (approximately 0.1 μg/N·m) were achieved at 20 g/l of urea concentration.

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