Electrochemical studies on aniline-pentamer-based electroactive polyimide coating: Corrosion protection and electrochromic properties

In this study, electrochemical investigations of corrosion protection and the electrochromic properties of an aniline-pentamer-based electroactive polyimide (AP-based EPI) coating prepared by oxidative coupling polymerization are presented. The in situ chemical oxidation of the reduced form of soluble, electroactive poly(amic acid) (EPAA) in N-methyl-2-pyrrolidone (NMP) was monitored by UV-Vis absorption spectra. Moreover, the electroactivity of the AP-based EPI was evaluated by performing electrochemical CV studies. Based on a series of electrochemical measurements in 3.5 wt% NaCl electrolyte, the AP-based EPI coating was found to exhibit enhanced corrosion protection effects on cold-rolled steel (CRS) electrodes as compared to the corresponding non-electroactive (NEPI) coating. A possible mechanism for the enhanced corrosion protection of EPI coatings on the CRS electrode has been proposed as follows: (1) EPI coatings may act as a physical barrier and (2) the redox catalytic properties of the aniline pentamer units in EPI may induce the formation of a passive metal oxide layer on the CRS electrode, as evidenced by SEM and ESCA studies. The electrochromic performance of EPI was investigated by measuring electrochromic photographs and UV absorption spectra. (C) 2011 Elsevier Ltd. All rights reserved.