Surface resistivity/conductivity of different organic-thin films by a combination of optical shearography and electrochemical impedance spectroscopy

Optical shearography and electrochemical impedance spectroscopy (EIS) were used for the first time to measure the surface resistivity/conductivity of different organic-thin films. Different organic coatings i.e., ACE Premium-gray, white, and beige Enamels (spray coatings), on a metallic alloy, i.e., a carbon steel, were investigated at a temperature range between 20–60 °C. The investigation focused on determining the in-plane displacement of the coatings with respect to the applied temperature range by optical shearography. Then, the AC impedance (resistance) of the same coated samples was determined by the technique of EIS in 3.5% NaCl solution at room temperature. In addition, a mathematical model was developed in order to obtain a proportionality constant (surface resistivity = ρ or conductivity = 1/ρ) between the determined AC impedance and the in-plane displacement. The obtained values of ρ of all investigated coatings, 0:25 × 10⁸–0:27 × 10¹⁰ Ωcm was found in the insulator range.