The preparation of a hydrochromic film and its application in the visualization of localized corrosion

Purpose The purpose of this study is to investigate the influence of different polarization potentials on the properties of the poly(2,5-dimethoxyaniline) (PDMA) films and use PDMA film for detecting local corrosion in situ, in a non-destructive and highly sensitive manner. Design/methodology/approach In this study, PDMA films were prepared on L245 carbon steel by potentiostatic polarization. Electrochemical hydrogen charging was used to investigate the influence of different polarization potentials (0.6, 0.8 and 1.0 V/SCE) on the properties of the PDMA film. In the subsequent research of this paper, a constant potential polarization condition of 0.8 V/SCE was selected for preparing the PDMA film, and the corrosion-induced hydrogen permeation of L245 samples in 3.5 Wt.% NaCl solution at different pH 4, 5 and 6 was examined. Findings The electrochemical hydrogen charging results indicate that the responsiveness of the PDMA film decreases as the preparation potential increases, while the contrast of the PDMA film increases with the preparation potential. The visualization of hydrogen experiment results show that as the corrosion proceeds, the PDMA film gradually brightens, and the area and degree of brightness also gradually expanded. Notably, the areas of corrosion sites are highly consistent with the regions of color change in the PDMA film in spatial location. Originality/value The results of this study provide a new way for local corrosion monitoring.