Life Prediction of Thin Organic Films by a Combination of Digital Shearography and Electrochemical Impedance Spectroscopy

摘要

A critical (steady state) value of the conductivity of different organic coatings was determined by a combination of digital shearography and electrochemical impedance spectroscopy (EIS). The behavior of organic coatings, i.e., ACE premium-gray enamel, white enamel, beige enamel (spray coatings), a yellow acrylic lacquer, and a gold nail polish on a metallic alloy, i.e., a carbon steel, was investigated over a temperature range of 20-60℃. The value of the conductivity of coatings was determined by correlating the in-plan displacement of the coating (by shearography over a temperature range 20-60℃) and the value of the alternating current impedance of the coating by EIS in 3% NaCl solution. The integrity of the coatings with respect to time was assessed by comparing the measured value of conductivity to the critical (steady state) or asymptotic value of conductivity. In other words, by shearography, measurement of coating properties could be performed independent of parameters such as UV exposure, humidity, presence of chemical species, and other parameters which may normally interfere with conventional methods of the assessing of the integrity of coatings. Therefore, one may measure the conductivity of coatings, regardless of the history of the coating, in order to assess the integrity of coatings. Also, the obtained shearography data were found to be in a reasonable trend with the data of EIS in 3% NaCl solution.