Effects of cerium based conversion coatings on the corrosion resistance of AZ31 magnesium alloy

Mg AZ31 alloy was chemically treated by a series of room temperature cerium conversion coatings without and with poly vinyl alcohol (PVA) as a green corrosion inhibitor and amino trimethylene phosphonic acid (ATMP). The effects of inhibitors on the morphological properties of the cerium film precipitated on the magnesium alloy surface were studied by scanning electron microscope (SEM). Potentiostatic polarization test was done in order to evaluate the corrosion resistance of the samples treated by Ce, Ce-PVA and Ce-ATMP in 3.5 wt.% NaCl solution. Results show that addition of PVA to the Ce bath could slightly increase the corrosion resistance of the magnesium alloy compared to the sample treated by Ce coating. Also, it was found that using ATMP did not result in higher coating corrosion inhibition properties. Moreover, less Ce deposit formed on the Mg AZ31 surface in the presence of PVA compared with other samples.