Abstract: he side reaction of coal indirect liquefaction unit may generate corrosive media such as small molecule organic acids. In order to ensure that the corrosion is controllable, a large number of stainless steel is used in the equipment of the unit, which will lead to a substantial increase in investment.This paper discusses the corrosion characteristics of carbon steel in different media through analyzing the on-site corrosion coupon test results. From the preliminary test results, it can be seen that the corrosion of light oil medium is mild, and there is a feasibility of using carbon steel. However, the corrosion of synthetic water medium is obvious, and carbon steel does not meet the requirements for long-term operation. The above conclusions can provide the basis for more reasonable material selection for the subsequent construction of coal indirect liquefaction units.

Key words: coal indirect liquefaction unit, small molecule organic acid, corrosion, material selection