Optimization of AC impedance test cell for accelerated evaluation of marine industrial coating in Kuwait

In previous studies a new AC impedance test cell has been designed for the evaluation of coating systems. In the present work, the viability of the test cell has been investigated on a selection of commercial quality coating systems. This is made in order to achieve an accelerated evaluation and proper prequalification of marine industrial coating arriving at the desalination industry and off shore pipeline marine structure in the state of Kuwait. The AC impedance behavior of three coating systems, fusion bonded epoxy, high build epoxy (HBE), and polyurethane were examined under the new test cell in 5% NaCl solution. The same test was supported by salt spray fog test and QUV for 1,000 h at 357deg;C (ASTM B117). Triplicate samples of each coating system were retrieved from the salt fog cabinet for impedance measurements after 500, 750, and 1,000 h. The same specimens were also examined for gloss retention and FTIR. The overall results of impedance and capacitance obtained with the modified test cell showed typical AC impedance spectrums that have proven its importance as an accelerated quantitative testing cell when combined with salt spray cabinet testing. The screening program has indicated that HBE is the best performed coating for values of impedance Rp = 8.53×109Ω and capacitance Cc = 4.52×10-12 F. ©2013 Desalination Publications. © 2014 Elsevier B.V., All rights reserved.