Enhancing the biodegradability and surface protective performance of AZ31 Mg alloy using polypyrrole/gelatin composite coatings with anodized Mg surface

The intention of the current study is to improve the biodegradability and corrosion resistant performance of AZ31 Mg substrates by anodization and electrodeposition of polypyrrole/gelatin composite coatings. The effect of anodization time, and the concentration of gelatin on the biodegradability and corrosion protective performance of coated AZ31 Mg substrates were systematically evaluated using different characterization techniques. Surface topographical and morphological studies of anodized substrates indicated that the surface roughness, distribution of pores and pore size increased with increasing the anodization time. Water contact angle studies confirmed the improved surface wettability of AZ31 Mg substrates after anodization treatment. Surface characterization results of PPy/Ge composite coatings revealed the significant influence of gelatin addition on the surface morphology of PPy coatings. Structural characterization results confirmed that intermolecular chemical interaction exists between the polypyrrole moiety and gelatin molecules. It was also found that the anodized layer has enhanced the adhesion of PPy coatings from 3B to 5B. In vitro corrosion analysis indicated that the anodization layer efficiently improved the corrosion resistance behavior of coated AZ31 Mg substrates and this performance was increased with the addition of gelatin up to 1 wt% and then slightly reduced. Hydrogen evolution measurements corroborated that the amount of hydrogen evolved is significantly reduced in the presence of anodization layer and gelatin addition into PPy coating.