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

CO:z 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 C02 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 C02 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 1 bar. 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 SOppm. 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 SOppm
dosage yields an inverse result in comparison to the results of uninhibited and 2Sppm Cl
corrosion test. It is concluded that the corrosion rate of X52 increases with NaCI
concentration and 25ppm is the optimum working dosage of the corrosion inhibitor.