Abstract
Optical shearography techniques 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 simulating the severe weather temperatures in Kuwait, especially between the daylight and the night time temperatures, 20–60 °C. The investigation focused on determining the in-plane displacement of the coatings, which amounts to the thermal deformation (strain) with respect to the applied temperature range. Then, the alternating current (AC) impedance (resistance) of the coated samples was determined by the technique of electrochemical impedance spectroscopy (EIS) in 3.5 % NaCl solution at room temperature. In addition, a mathematical model was derived in order to correlate between the AC impedance (resistance) and to the surface (in-plane) displacement of the samples in solutions. In other words, a proportionality constant (surface resistivity or conductivity=1/ surface resistivity) between the determined AC impedance (by EIS technique) and the in-plane displacement (by the optical interferometry techniques) was obtained. Consequently the surface resistivity (ρ) and conductivity (σ) of the coated samples in solutions were obtained. Also, electrical resistivity values (ρ) from other source were used for comparison with the calculated values of this investigation. This study revealed that the measured values of the resistivity for the ACE Premium- gray, white, and beige coatings were carried out for the first time. No data on the values of (ρ) were found in literature for the same coatings, using direct current (DC) methods. However, the value range of (ρ) of all investigated coatings, 0.25x108 - 0.27x1010 Ω-cm was found in the insulator range.
