This work is an extension of a program reported in 1984 to establish factors which control corrosion of API line pipe in gas containing carbon dioxide and water. In this phase of the program, there were four objectives. One was to establish the temperature of maximum corrosion in the range of 75°, 100° and 175°F at 1000 psi in water saturated with carbon dioxide at partial pressures of 15 and 50 psia. The next was to explore the role of carbon content and microstructure in the steel, iron carbonate film formation, and resulting corrosion rates. The third was to examine the role of pre-existing...
This work is an extension of a program reported in 1984 to establish factors which control corrosion of API line pipe in gas containing carbon dioxide and water. In this phase of the program, there were four objectives. One was to establish the temperature of maximum corrosion in the range of 75°, 100° and 175°F at 1000 psi in water saturated with carbon dioxide at partial pressures of 15 and 50 psia. The next was to explore the role of carbon content and microstructure in the steel, iron carbonate film formation, and resulting corrosion rates. The third was to examine the role of pre-existing mill scale and corrosion films on accelerating pitting attack. The final objective was to extend a spread sheet computer model to calculate corrosion rates from field data. Tests were run in a refreshed, recirculating autoclave at a total pressure of 1000 psi in water saturated with CO2 at partial pressures of 15 and 50 psia, and containing bicarbonate ion to adjust the pH either to 5 or 6. Six materials were tested: ASTM-A53B, two lots of API5LX-X52 and three lots of API5LX-X60. Samples were pulled at intervals for weight loss corrosion and to examine the surface films by electron microscope and metallography. After plotting the weight loss results, corrosion rates in mils per year (MPY) were calculated. The microstructure of the metal, the corrosion films of iron carbonate, and the weight loss results were then examined. The corrosion data were incorporated into a spread sheet computer model for users to calculate their own pipe line corrosion rates.