Abrasion resistance of magnesium alloys with surface films generated from phosphonate imidazolium ionic liquids

Surface films formed by treatment with the ionic liquids (ILs) 1,3-dimethylimidazolium methylphosphonate (LMP101), 1-ethyl-3-methylimidazolium methylphosphonate (LMP102) and 1-ethyl-3-methylimidazolium ethylphosphonate (LEP102) on magnesium alloys have been studied. The abrasion resistance of the coated alloys was studied by microscratching under progressively increasing load, and compared with that of the uncoated materials. Abrasion-protective phosphorus-containing films are generated on AZ31B, with an order of abrasion resistance as a function of the IL of LEP102 > LMP101 > LMP102, with a reduction in penetration depth of a 67% for the sample treated with LEP102 with respect to the uncovered alloy. This is attributed to the formation of a continuous adhered phosphorus-containing film. In contrast, the abrasion resistance of EZ33A alloy is not improved due to the presence of the less reactive Zn-rich phase at the grain boundaries, which prevents the formation of a continuous protective layer. The results are discussed from contact angles, SEM-EDX and XPS analysis.