Effect of extremely high CO(2) pressure on the formation of the corrosion film on 13Cr stainless steel

The corrosion behaviors of 13Cr martensitic steel under different CO(2) partial pressures (4–28 MPa) were investigated by weight loss tests and surface characterizations. The results show that the corrosion rate of 13Cr steel shows a sharp increase under higher CO(2) pressure (28 MPa), which reached approximately 20–180 times as large as those under lower CO(2) pressures (4–12 MPa). Under the lower CO(2) pressures, a single-layered Cr(OH)(3) passive film forms and completely covers the steel surface. However, when the CO(2) pressure reaches 28 MPa, a very different corrosion film which contains an inner Cr(OH)(3) passive layer and an outer FeCO(3) layer forms, and the inner passive layer shows local damage. This phenomenon can be explained by the lower pH (∼2.75) and the higher H(2)CO(3) concentration in the solution under the higher CO(2) pressure.