Electrochemical impedance spectroscopy as a rapid technique for evaluating the failure of fusion bonded epoxy powder coating

Abstract The internal epoxy powder coating of land surface oil pipeline (LSP) was completely detached, curling from the substrate, and the production flow line was plugged with the deposit of paint debris after one year of operation in service. The failure has been identified, by differential scanning calorimetry (DSC) and other surface analytical techniques, as curling caused by the improper curing process of the powder coating materials. In the present study, an experimental investigation was carried out using electrochemical impedance spectroscopy (EIS) by employing a new test cell to find out the reason behind the failure of the internal coating. The EIS was used to analyze the causes of failure of two different batches of the same coated piping, as-received epoxy coating and the failed one, by simulating the necessary environment and operation temperature. The EIS results with the new test cell indicated the compliance of the technique in confirming the hypothesis, obtained about the poor quality of the powder coating process and adhesion loss failure, obtained by the DSC, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) techniques. The study confirmed that the quality of coating could be identified through the impedance value of the intact and failed coatings.