Study of N80 Steel Corrosion in the Oil-gas-water System Containing CO_2 and H_2S

The corrosion regularity of N80 steel in the oil-gas-water systerm containing CO2 and H2S was studied by static weight-loss method and potentiodynamic scanning method.To a certain extent,the static weight-loss method tests showed that little amount H2S restrains N80 steel corrosion.At a certain temperature,the corrosion rate of N80 steel initially was lower and then higher when the concentration of H2S continued to increase.With the same concentration of H2S,the corrosion rate of N80 steel initially was higher and then lower when the temperature raised.The corrosion rate of N80 steel reached the maximum value at about 60℃.Under dynamic conditions,potentiodynamic scan studies shows that in the oil-gas-water co-existing non-homogeneous medium,N80 steel corrosion is greatly influenced by the partial pressure ratio of CO2/H2S.At 50℃,in the oil-gas-water co-existing solution,when the partial pressure ratio of CO2/H2S is less than 20,the corrosion rate of N80 steel is controlled by the amount of hydrogen sulfide.When the partial pressure ratio of CO2/H2S is more than 500,the corrosion rate of N80 steel is controlled by the amount of carbon dioxide;when the partial pressure ratio of CO2/H2S is between 20 and 500,the corrosion rate of N80 steel is controlled by the amount of carbon dioxide and hydrogen sulfide.