Influence of pH on the synthesis and properties of polypyrrole on copper from phytic acid solution for corrosion protection

• Adhesive and protective PPy film was obtained in phytic acid solution with a wide range of pH.
• Thickness of the protective Cu-phytate phosphate was dependant on solution pH.
• PPy formed in pH 4 phytic acid solution inhibited the copper dissolution by 1/200.
• The PPy with higher oxidized degree was formed in phytic acid solution with a lower pH.

Polypyrrole (PPy) films were deposited on copper from “green” inhibitor of phytic acid solution for corrosion protection of copper. The corrosion protection property of the PPy layer was studied by an immersion test in a NaCl aqueous solution. The polymerization process of PPy on copper changed with the pH values of phytic acid solution and current density applied. When one oxidized bare copper in phytic acid solution at various pHs containing pyrrole monomer, a thin layer consisting of complex compound of Cu-phytate was firstly formed, followed by the formation of the PPy layer doped with phytate anion on the complex compound layer. The complex compound layer passivated the copper surface and its thickness increased with the lower pH value of the solution and the lower current density applied. It was found that the PPy coating prepared in the phytic acid solution at pH 4 exhibit the most protective property against copper corrosion.