Interfacial study of the formation mechanism of corrosion resistant strontium phosphate coatings upon Mg-3Al-4.3Ca-0.1Mn

Strontium phosphate (SrPO4) conversion coatings with the ability to impart significant corrosion resistance were prepared upon magnesium alloy Mg-3Al-4.3Ca-0.1 Mn (wt.%). Scanning electron microscopy equipped with energy dispersive spectroscopy and transmission electron microscopy were also employed to characterise surface and interfacial morphology, along with the composition of the coatings. The protective performance of SrPO4 coatings was examined by potentiodynamic polarisation curves and immersion testing. A coating-growth mechanism was proposed and correlations between processing parameters and coating quality was established. The findings herein provide new insights for design of environmentally-benign and corrosion resistant coatings upon magnesium alloys through a simple chemical conversion technique.