A STUDY OF ACETIC ACID ROLE IN CO2 CORROSION

CO2 corrosion caused by carbonic acid that formed when CO2 gas dissolved in the water or brine that accompanies oil production at high pressures common in underground oil and gas reservoirs. Usually, CO2 corrosion problems are manageable and under control. However, when small amount of organic acid that dominated by acetic acid is present in the system, the corrosion rate changes drastically. In this project, Electrochemical Impedance Spectroscopy ( EIS ) and Linear Polarization Resistance ( LPR ) was the measurement technique that being used in the project. EIS is a technique employed to study the mechanisme of CO2 corrosion in presence of acetic acid, while LPR is a technique to determine the corrosion rate. All experiments were conducted in a 3% NaCl solution of pH 5.5 and temperature 60˚C.Based from results that was gathered from the experiment, LPR shows that corrosion rate for 1000ppm and 2000ppm of acetic acid increased significantly compared to blank CO2. Meanwhile for 4000ppm, the corrosion rate decreased. This phenomenon was due to excessive non ionized acetic acid HAc. The carbonate ions from the iron carbonate could not dissolve the excessive amount of acetate leaving the iron ions to reacts with it and form iron acetate. Formation of FeCO3 that decrease the corrosion rate can be proven from the trend of the data collection that shows significant decrease with time. It is correct to claim that in presence of acetic acid, the corrosion rate could increase significantly.