Corrosion Behavior of AZ91D Magnesium Alloy with a Calcium–Phosphate–Vanadium Composite Conversion Coating

Abstract

A novel self-healing calcium–phosphate–vanadium (Ca–P–V) composite coating on Mg alloy was successfully fabricated through a chemical conversion method. The effects of the vanadium concentration on the anticorrosion property of the substrate were also tested. The Ca–P–V coating with the main composition of CaHPO4, Ca3(PO4)2, and Mg3(PO4)2, with some hydroxides of V(V) dispersed into it has a similar morphology to the single vanadium coating. The corrosion behaviour of the Ca–P–V coating was studied through the electrochemical tests and the scratch immersion test in 3.5 wt % NaCl solution. The results showed that the Ca–P–V coated samples not only exhibit good corrosion resistance property, but also show self-healing ability. The ions of Ca, P, and V released from the coating can migrate in the corrosion solution and form a new compound layer on the damaged zone.

An Impact of the Recent Developments in Coating Materials and Techniques on the Corrosion Response of AZ91D Alloy: A Review

“…[77][78][79] Comparatively, sol-gel coatings can easily be applied to large surfaces with better uniformity. The composite materials coated AZ91D alloy has been explored for many applications, [80][81][82][83][84][85][86] which is schematically represented in Figure 8.…”

Corrosion and Protection of Magnesium Alloys: Recent Advances and Future Perspectives

“…The corrosion resistance of several phosphate conversion coatings (MgP, ZnP, and CaP) on magnesium alloy substrates was investigated [96], and the results were as follows: coating thickness: ZnP > CaP > MgP; compactness: MgP > CaP > ZnP; and long-term corrosion resistance: ZnP > CaP > MgP. An innovative self-healing calcium vanadium phosphate (Ca-P-V) composite coating was successfully created by Sun et al Figure 12 shows the formation mechanism of the composite coating [107]. The film not only demonstrates excellent corrosion resistance but also possesses self-healing capabilities.…”