The Effect of Temperature and Concentration on Corrosion Inhibition of Mild Steel in Carbon Dioxide Saturated Solution

CO2 corrosion is the main threat in oil and gas industry. In order to reduce the corrosion of carbon steel pipelines in CO2 environment, inhibitors are added to control corrosion rate to an acceptable level. However, the successful of the corrosion inhibitor injection depends not only on the good inhibitor formulation used but also operational parameters such as temperature, pH and its concentration. The objective of the project is to investigate the effect of ethanolamine on the corrosion rate for mild steel in CO2 environment. Temperature and corrosion inhibitor’s concentration are varied from 25°C to 80°C and 250ppm to 500ppm respectively. The corrosion inhibitor used is ethanolamine and pH is set at 5. The test medium is 3% NaCl solution saturated with carbon dioxide gas at 1 bar. From the experiment, it is found that the efficiency of inhibitor decreased when temperature increases from room temperature 25°C to 80°C. The highest efficiency of inhibitor is at room temperature and inhibitor concentration at 500ppm with the value of 96.4%. However, at temperature 80°C and concentration of ethanolamine at 250ppm, the inhibitor efficiency is the lowest with the value of 72.8%. This is possibly due to the active sites blocking effect and it will discuss later on the Chapter 4. The recommendations are to do further testing to simulate the turbulence flow condition and to investigate the formation of corrosion product film at higher pH that affects the efficiency of the inhibitor.