Properties of ZnO/ZnAl2O4 composite PEO coatings on zinc alloy Z1

Recently the successful formation of PEO coatings on zinc alloy in a phosphate aluminate electrolyte was shown. The produced composite coatings contain various mixtures of ZnO and ZnAl2O4. In frame of the current study, the properties of the formed coatings including adhesion/cohesion, wear, corrosion and photocatalytic activity were analysed to identify possible applications. However, the coatings show internal porosity and a sponge-like structure. Thus the cohesion within the coating is quite low. Pull-off tests have demonstrated clear rupture within the PEO layer at strength values as low as 1 MPa. The photocatalytic activity is limited, in spite of the formation of a higher amount of ZnO at shorter treatment times. Interestingly, the composite coatings of ZnO and higher amounts of ZnAl2O4 spinel showed a higher activity, but not sufficient for fast and effective catalytic cleaning applications.

Automated summary

PEO coatings were successfully formed on zinc alloy in a phosphate aluminate electrolyte, containing varying mixtures of ZnO and ZnAl2O4. The coatings showed internal porosity and low cohesion, limiting their photocatalytic activity. Composite coatings of ZnO and ZnAl2O4 spinel displayed higher activity but were not sufficient for fast and effective catalytic cleaning applications.