Corrosion Behavior Research Of Cr13 Steel In Environment With CO₂/H₂S

With the development of oil and gas industry, strong corrosive medium containing CO2 and H2S has brought serious challenges. Oil production fluid containing CO2, H2S, corrosive anions and scale cations as well as others cause steel corrosion under temperature and pressure during oil production. Serious corrosion of 13Cr steel having good corrosion resistance would be caused by the rising concentrations of H2S and CO2 with the development of oilfields. However, currently a few papers about corrosion mechanism of 13Cr steel have been published. Therefore, it is imperative to comprehensively study the corrosion behavior of 13Cr steel used in oilfield. In this work, the mechanism and main influence factors on 13Cr steel in CO2-H2S saturated solution were systematically studied using weight loss method, electrochemical measurement techniques and surface analytical technology. The main conclusions are as follows:1 The mechanism and influencing factors of 0Cr13 steel corrosionThe corrosion of 0Cr13 and 2Cr13 steel is controlled by anodic in CO2 solution.0Cr13 steel can passivating in this environment. Cl-concentration and temperature can affect pitting potentials. The increases of them reduce pitting potentials. It can make pitting corrosion occurrence and development.2 The electrochemical behavior of 0Cr13 steel with CO2/H2S medium is activation dissolved, With the increase of H2S content, the corrosion rate of 0Cr13 steel changed in the shape of saddle and reached the minimum value at 0.015mol·L-1. As temperatures rising, corrosion rate of 0Cr13 steel in CO2/H2S system are presented first, then decreased, when the temperature is 70℃, corrosion rate of 0Cr13 steel reaches maximum. Temperature also have an effect on the corrosion products, corrosion products are mainly Fe7S8 at 50℃and mainly Fe1-xS at 150℃. With the increase of the concentration of Cl-, corrosion rates of 0Cr13 of steel present the saddle type conversion.3 The electrochemical behavior of 2Cr13 steel with CO2/H2S medium is activation dissolved. The electrochemical reactions of 2Cr13 steel are controled by cathode reaction which occurred concentration polarization controlled. H2S concentration has a significant effect on corrosion rates of 2Cr13 steel in H2S/CO2 system. With the increase of H2S concentration, corrosion rate increased rapidly, but H2S concentration has no significant effect on the corrosion products. Temperature has also a significant effect on corrosion rates of 2Cr13 steel. Corrosion rates are increased with the temperature rise. Different temperatures generated corrosion products and components of dense membranes are not the same. Corrosion products are mainly FeSat 50℃and mainly Fe1-xS at 150℃. With the increase of the concentration of Cl-, corrosion rates of 0Cr13 of steel present the saddle type conversion and reached the maximum value at 50g·L-1.