Electrochemical studies for the electroactivity of amine-capped aniline trimer on the anticorrosion effect of as-prepared polyimide coatings

The electroactive polyimide consisting of various content of amine-capped aniline trimers (ATs) have been successfully synthesized and characterized by Fourier-Transformation infrared and UV–visible absorption spectroscopy. The electroactivity of as-prepared polyimides was tested by electrochemical cyclic voltammetry (CV) studies. It was noticed that the as-prepared electroactive polyimide with higher content of amine-capped ATs shows higher electroactivity (i.e., larger redox current) than that of non-electroactive polyimide, leading to enhance corrosion protection efficiency on cold-rolled steel (CRS) electrodes. This enhanced corrosion protection efficiency has been explained based on a series of electrochemical measurements such as corrosion potential, polarization resistance, corrosion current and electrochemical impedance spectroscopy (EIS) studies in 5 wt-% NaCl electrolyte. This significant enhancement of corrosion protection on CRS electrodes as compared to non-electroactive polyimide might probably be attributed to the redox catalytic property of as-prepared electroactive polyimide coatings inducing the formation of passive layer of metal oxide.