Effect of thiosulphate/H₂S on crevice corrosion behaviour of P110 carbon steel in CO₂-saturated solution

Abstract

The effect of thiosulphate/H 2 S on crevice corrosion behaviour of P110 carbon steel in the CO 2 -saturated 3.5 wt% NaCl solution was investigated. The results showed that crevice corrosion of P110 steel could not occur in the CO 2 -saturated solution, likely due to the inhibition of both anodic and cathodic reactions inside crevice. Further, the structure of corrosion product film along the crevice wall is influenced by the concentration of thiosulphate. Increasing the concentration of thiosulphate to 10 −2 mol L −1 promotes the formation of fine flake-like mackinawite outside crevice. In addition, crevice corrosion of P110 steel in the CO 2 -saturated solution is promoted by increasing the concentration of thiosulphate. This is because the dense and fine mackinawite film on the steel surface has a better protectiveness and could enhance cathodic reaction rate outside crevice.

Effect of stress on the crevice corrosion of P110 steel in the CO2-saturated NaCl solution containing thiosulphate/H2S

“…Before heating up the autoclave, 2 L of solution was deoxygenated by bubbling N 2 gas into the autoclave for 3 h. Following the deoxygenation, pure CO 2 was directly injected into the autoclave until the pressure reached to 2 MPa. Then the autoclave was heated up to 90°C and maintained at this temperature for 240 h. The pH of the solution is about 3.3 [3].…”

“…The failure of down-hole tubings, due to the crevice corrosion of pipe couplings, is a threat to the safety of oil and gas production [1,2]. Crevice corrosion in oil and gas field environments is attributed to the galvanic effect between the steels inside and outside crevice [3][4][5]. Studies have revealed that H 2 S [3], acetic acid [4][5][6], oxygen [7][8][9], crevice geometry [10], inhibitors [9,11], alloying elements [11,12] and sulphate-reducing bacteria [13][14][15] are key factors affecting the crevice corrosion.…”

“…Crevice corrosion in oil and gas field environments is attributed to the galvanic effect between the steels inside and outside crevice [3][4][5]. Studies have revealed that H 2 S [3], acetic acid [4][5][6], oxygen [7][8][9], crevice geometry [10], inhibitors [9,11], alloying elements [11,12] and sulphate-reducing bacteria [13][14][15] are key factors affecting the crevice corrosion. Several investigations showed that no crevice corrosion occurred in the CO 2 -saturated solution [12] while bubbling H 2 S or adding acetic acid into the solution could promote the initiation of crevice corrosion [3][4][5]11].…”

“…Studies have revealed that H 2 S [3], acetic acid [4][5][6], oxygen [7][8][9], crevice geometry [10], inhibitors [9,11], alloying elements [11,12] and sulphate-reducing bacteria [13][14][15] are key factors affecting the crevice corrosion. Several investigations showed that no crevice corrosion occurred in the CO 2 -saturated solution [12] while bubbling H 2 S or adding acetic acid into the solution could promote the initiation of crevice corrosion [3][4][5]11]. The increase of cathodic reaction outside crevice as a result of higher concentration of acetic acid, led to a greater galvanic effect between the inside and outside crevice, and therefore, promoted crevice corrosion of the carbon steel [5].…”

“…A number of studies showed that the presence of a small amount of H 2 S/thiosulphate promoted SCC obviously and the corrosion pits were commonly crack initiation sites by slow strain rate tensile/bending tests [25][26][27]. Moreover, crevice corrosion of P110 steel in the CO 2saturated solution was triggered by a small amount of H 2 S/ thiosulphate [3]. However, few experimental data on the crevice corrosion behaviour of P110 steel under stress in H 2 S/ CO 2 sour environment has been reported.…”