The Effects of Fluid Working Conditions on Flange Face Corrosion

Abstract

Abstract The second most common cause of hydrocarbon leakage is corrosion in offshore platforms. In seawater and hydrocarbon services, bolted flange joints can be susceptible to corrosion at their flange face. The current work considers corrosion of bolted flanged gasketed joints using the COQT fixture (COrrosion Quantification Test) to evaluate corrosion in flange faces. According to the literature, both crevice corrosion and galvanic corrosion widely occur in bolted flanged gasketed connections, creating leakage paths of the pressurized fluid. Leakage failure in bolted flanged gasketed joints can cause hazards to the environment and human safety. Corrosion in bolted gasketed joints was investigated in the literature. However, these studies do not consider the influence of the operating parameters such as fluid flow, pressure, pH, conductivity, temperature, and gasket contact pressure. With the developed COQT fixture, which was introduced in the previous paper, different electrochemical techniques can be applied to measure flange corrosion under controlled test conditions. The polarization technique will be used to measure and compare the corrosion rate of flange at different fluid flow rates, and gasket contact stresses. The flange sample material is ASTM A105, and the gasket material is Teflon. Electrochemical tests are conducted with a solution of 3.5% NaCl. Confocal microscopy is used to visualize the morphology of the damaged zones on the surface, and localize and quantify the pits size caused by corrosion, respectively. Comparing the results of the electrochemical tests and the microscopic studies will identify the most influent factor on the corrosion rate of flanges.