Polymer plating on AZ31 magnesium alloy surface and film evaluation of corrosion property

The polymeric thin film was prepared on the surface of AZ31 magnesium alloy by polymer plating of 6-dihexylamino-1,3,5-triazine-2,4-dithiol monosodium (DHN) in order to modify its surface feature and to improve its anti-corrosive property. Cyclic voltammetry was used to study the electrochemical reaction and film growth process of poly(6-dihexylamino-1,3,5-triazine-2,4-dithiol) (PDH) film, and the reaction peaks for film formation and growth were affirmed. The polymeric film weight was determined by electronic balance and its insoluble fraction in tetrahydrofuran was also measured. Contact angle meter was applied to test the surface wettability with distilled water drops at ambient temperature. It was found that the polymer-plated AZ31 alloy showed hydrophobic property with its distilled water contact angle up to 117.2°. The performance property of polymeric thin film formed on AZ31 surface was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in the corrosion solution of 3.5% NaCl. The electrochemical experiment results showed that polymer-plated thin film with hydrophobic and insulative characteristics could provide surface modification and an effective anti-corrosive protection to magnesium alloy substrate compared to the blank one.