Study of Carbon Dioxide Corrosion on Carbon Steel at Different Salt Concentrations

CO2 corrosion is a major threat in the oil and gas industry. Several possible mitigation methods have been developed to reduce the corrosion rate in these pipelines to acceptable levels. In order to reduce the corrosion of carbon steel pipelines in CO2 environment, inhibitors are added to control corrosion rate to an acceptable level. The usage of the corrosion inhibitor is an economical and flexible method while being widely used in various applications. Corrosion inhibitor is a chemical compound which is added to the fluid phase and has an effect on the metal surface. The effectiveness of the corrosion inhibitor does not only depend on the inhibitor formulation but also on operational parameters such as temperature, pH and flow conditions. Pipelines in the oil and gas industry are located in seawater environment which is a natural corrosive environment. The objective of this project is to investigate the influence of salt concentration towards the corrosion rate of carbon steel in CO2 environment that has been added with corrosion inhibitor. The temperature and pH used for this study is 60°C and 4.0pH. The NaCl solution concentration are varied to 1%, 3%, 5%, 10% and 20%. The test medium is saturated with carbon dioxide gas at 1bar. The concentration of the corrosion inhibitor is also applied to see the effect of corrosion inhibitor concentration to the corrosion rate. The inhibitor used is AMTECH and of dosages 25ppm and 50ppm. The material used for this study is carbon steel X52. Results of the inhibited corrosion tests reveals at 25ppm the corrosion rate of X52 is the lowest. Meanwhile the corrosion rate of X52 at 50ppm dosage yields an inverse result in comparison to the results of uninhibited and 25ppm CI corrosion test. It is concluded that the corrosion rate of X52 increases with NaCl concentration and 25ppm is the optimum working dosage of the corrosion inhibitor.