The effect of Mg alloy substrate on “electroless” E-coating performance

The corrosion performance of “electroless” E-coating pre-film on eight different Mg alloys is compared in a 5 wt.% NaCl. The results show that the alloys have different levels of surface alkalization effect, resulting in different thickness of films formed on the alloys. The alloying elements in a Mg alloy do not directly influence the film formation and corrosion performance. Instead, the corrosion resistance of substrate has a significant effect on the degradation or corrosion process of the coated Mg alloy. The corrosion resistance of the substrate Mg alloy can influence the porosity of pre-film during “electroless” E-coating deposition, and it is also a critical factor determining the film corrosion degradation.

► We apply a recently developed “Electroless” E-coating to 8 Mg alloy surfaces.
► On different Mg alloys, the coatings have different thickness and porosities.
► The coating is much corrosion resistant on a corrosion resistant Mg alloy.
► We explain the dependence of coating quality on the substrate activity.