ACTIVATION/REPASSIVATION BEHAVIOR OF 13Cr IN CO_2 AND SAND ENVIRONMENTS USING A MODIFIED ELECTROCHEMICAL NOISE TECHNIQUE

摘要

While 13Cr is commonly used in highly corrosive CO_2 environments in the oil and gas industry, the behavior of 13Cr in a combined CO_2 corrosion and sand erosion environment is not well understood. Key questions include, under what conditions will sand remove the passive oxide layer and how quickly is it repassivated? In order to understand the activation/repassivation behavior of 13Cr in real time, a modified electrochemical noise technique called the electrochemical emission spectroscopy (EES) is employed. Initial results indicate that the EES technique can provide real time information about the activation/repassivation behavior of 13Cr and monitor the severity of erosion-corrosion. The current between the working electrode and the micro-cathode is low if the test solution is sand free. When some amount of sand is added into the solution, potential drops suddenly, and at the same time, current increases dramatically. This is a behavior expected to occur when the passive film breaks down due to sand particle impingements. This phenomenon is observed whenever additional sand is inserted into the solution, which may indicate that the passive film is never completely removed by sand particles. It is also found that the sand concentration has a linear relationship with the current. This result suggests that the erosion-corrosion penetration rate may have a quantitative relationship with the current output.