Internal corrosion is a problem in wet natural gas gathering lines. Literature on the subject suggests that dissolved oxygen (O2) is one of the more corrosive contaminants in natural gas. Immersion tests, funded by a major gas transmission company, were performed on Cl018 (UNS G10180) specimens to assess the influence of O2 concentration on the internal corrosion of the wet gathering system in their storage field. Twenty-eight day tests were performed in a flow-through (gas phase only) autoclave at 70°F (21°C) and 1200 psi (8274 kPa) with simulated natural gas mixtures containing 10, 100, 500 and 1000 ppm ( by volume) O2. Specimens were exposed to the vapor, vapor/liquid (V/L) interface, and liquid phases of pure water and saltwater in these tests. The highest corrosion rate, based on groove depth, was measured for the V/L specimens in pure water with 1000 ppm O2. Corrosion rates, based on weight loss, generally maximized at an O2 concentration of 100 ppm.
Keywords: Corrosion, Natural Gas, Carbon Steel, Pipeline, Oxygen, Internal Corrosion, C1018