Characterization and Electrochemical Investigations of Polypyrrole/Aluminum Flake Composite Pigments on AA 2024-T3 Substrate

Abstract

Phosphate and nitrate doped Polypyrrole (PPy)/Aluminum (Al) flake pigments were synthesized by chemical oxidative polymerization method. Coatings were formulated from the phosphate doped PPy/Al flake pigment, nitrate doped PPy/Al flake, and as received Al flakes at 20% pigment volume concentration (PVC). The anticorrosion properties of coatings on aluminum alloy (AA 2024-T3) were monitored by exposure with accelerated salt spray (ASTM B117), electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET), and anodic polarization experiments. Phosphate and nitrate doped PPy/Al flake coatings showed enhanced anticorrosion ability in comparison with as received Al flake coating as observed in accelerated salt spray test. In the anodic polarization experiments, phosphate and nitrate doped PPy/Al flake coatings exhibited a positive shift in the potential suggesting the passivation of the substrate. Additionally, SVET experiments did not detect appreciable corrosion activity for the samples demonstrating better corrosion protection ability of phosphate and nitrate doped PPy/Al flake coatings.