L51468 Effect of Water Chemistry on Internal Corrosion Rates in Offshore Natural Gas Pipelines

The natural gas carried in pipelines often contains liquid water, carbon dioxide, hydrogen sulfide, and other components that cause internal corrosion of the carbon steel pipelines. To identify key variables that could affect the corrosivity of wet, sweet gas to carbon steel, the research program focused on the composition influences of specific contaminants and the effects of surface films, velocity and metallurgy of the pipe material.

The objective of this laboratory film research program was to identify key variables that could affect the corrosion of the inside surface of carbon steel gas pipelines carrying wet natural gas containing carbon dioxide. Forty-two autoclave tests of 8 to 21 days duration were conducted at 1000 psi pressure to measure the uniform corrosion rate of several grades of carbon steel as various changes were made in the water chemistry, CO2 partial pressure, temperature, and water velocity. Three gas pipeline companies provided pipe samples for pipelines exposed to wet CO2, and these were examined for corrosion.