Performance evaluation of some fusion-bonded epoxy coatings under water transmission line conditions

Abstract

The work presented in this paper deals with the performance evaluation of some fusion-bonded epoxy (FBE) coatings under water transmission line conditions. The work is aimed to evaluate corrosion–erosion behavior of selected FBE coatings in different product waters under simulated water transmission line conditions to find applications in sections of water transmission lines which are subjected to high flow, water hammer or turbulence. Three different FBE coatings, namely, Scotchkote 206 N, NAP-GARD 7–2500, and RESICOAT R4 Blue were considered for the studies. The studies were carried out in treated SWRO (seawater reverse osmosis) permeate and treated and untreated MSF (multistage flash) product water. To generate data about the erosion–corrosion resistance of the coatings under pipelines operating conditions, coated steel panels of fixed dimension were subjected to jet impingement test (JIT). ac impedance tests were carried out on the coated steel samples obtained after subjecting to JIT. The tests were carried out to evaluate qualitatively water uptake by the coatings. Adhesion test was carried out to assess the adhesive strength of the coatings. The monitoring of total organic carbon (TOC) in the test media, before and after subjecting of JIT, was also carried out. The extent of formation of TOC in the test media is indicative of the possible degradation/leaching of coatings under severe JIT conditions. All the three coatings subjected to JIT did not show any impingement damage, loss of adhesion, blistering damage or color changes, thus reflecting their excellent corrosion–erosion property. The effect of residual chlorine concentration on the corrosion–erosion property of the coatings appears to be insignificant. The results of ac impedance showed very high initial impedance for all the three coatings giving them excellent ratings. However, the performances of Scotchkote 206 N and NAP-GARD 7–2500 in treated SWRO permeate was found to be affected after 10 months immersion. The results of TOC monitoring indicated the presence of some organic compounds in the test media possibly due to the degradation/leaching of coatings under severe JIT conditions. The residual chlorine concentration in the test media appears to influence the formation of TOC. Therefore, further studies are needed to establish the safety of the coating from health point of view.