Effects of Rust Preventive Coating Applied to Flange Surfaces on Sealing Performance and Fluid Contamination

Abstract Corrosion on flange faces can occur during plant construction due to improper storage before assembly, and cases have been reported where corrosion was observed even after flange assembly. As a preventive measure, experimental studies have demonstrated that applying a wax-type rust preventive coating to flange faces is effective. Despite its potential benefits, concerns remain regarding its use during plant operation: (1) the possibility of reduced sealing performance, and (2) the risk of the coating dissolving into process fluids. To address these concerns, quantitative evaluations were conducted, including leak-tightness testing and both measurement and simulation of coating dissolution. The results demonstrated that the rust preventive coating does not compromise flange sealing performance, and the level of dissolution into internal fluids was found to be negligible. These findings provide a practical basis for leaving rust preventive coatings on flange faces without removal, offering a viable solution to corrosion management during plant construction and operation.