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Influence of monoethylene glycol on corrosion inhibitor of wet gas pipeline

This paper presents a study of MEG inhibition properties in acid gas with CO2 content of 4 mol. %, an influence of MEG content in the brine water, pH and temperature on the corrosion rate of carbon steel by linear polarization resistance (LPR) and mass loss methods. The results show that the more MEG content increases, the more corrosion rate decreases. However, this effect is not significant unless the MEG content in the bulk liquid phase is higher than 70 wt. %. | Vietnam Journal of Science and Technology 55 (5B) (2017) 246-256 INFLUENCE OF MONOETHYLENE GLYCOL ON CORROSION INHIBITOR OF WET GAS PIPELINE Nguyen Thi Le Hien*, Pham Vu Dung, Le Thi Hong Giang, Le Thi Phuong Nhung Vietnam Petroleum Institute, 167 Trung Kinh, Yen Hoa, Cau Giay, Ha Noi * Email: hienntl@vpi.pvn.vn Received: 31 August 2017; Accepted for publication: 9 October 2017 ABSTRACT In wet gas pipelines, monoethylene glycol (MEG) is widely used as a hydrate inhibitor, which can absorb free water and make decrease the corrosion rate of carbon steel pipeline. On the other hand, the presence of MEG affects on the solubility and diffusivity of CO2 in water. So, this paper presents a study of MEG inhibition properties in acid gas with CO2 content of 4 mol. %, an influence of MEG content in the brine water, pH and temperature on the corrosion rate of carbon steel by linear polarization resistance (LPR) and mass loss methods. The results show that the more MEG content increases, the more corrosion rate decreases. However, this effect is not significant unless the MEG content in the bulk liquid phase is higher than 70 wt. %. Keywords: monoethylene glycol, corrosion in CO2 environment, corrosion inhibition. 1. INTRODUCTION Natural gas in Vietnam is currently being exploited from 20 mines in three basins, such as Cuu Long, Nam Con Son, and Malay Tho Chu. The gas is transported by pipelines from the offshore system to the offshore or from the plant to the export port of refineries, etc. Such a large piping system when operating inevitable damage or defects caused by various causes, especially from within difficult to detect. Since subsea pipelines are surrounded by cold seawater, the water vapor originating from the gas reservoir condenses on the internal wall of the pipe and collects at the bottom of the pipe. This condensation is very corrosive, due to the presence of CO2 in the gas phase, which dissolves in the condensed water and forms carbonic acid (H2CO3) [1]. .