Laboratory study on metal corrosion by dimethylmercury

Abstract

As discovered dimethylmercury (DMM) is also one of organomercury compounds in natural gas, and the mercury metal is well known to drastically corrode natural gas pipelines and other accessories made from metal, such as aluminium heat exchanger. The objective of this work is thus to study the effect of the dimethylmercury compound on the corrosion of carbon steel and aluminium metal in the laboratory. Furthermore, rate and form of corrosion are also investigated as well. Absolute methanol and petroleum ether with the boiling point in the range of 80-100℃ were chosen as solvents to dissolve dimethyimercury. The results showed that after immersing carbon steel and aluminium specimens in the dimethylmecury solution for more than 700 h. at ambient temperature, aluminium specimens were remarkably corroded as compared to carbon steel, 9 times stronger, and the corrosion rate of aluminium specimens was also higher in the petroleum ether media Corrosion appearance was rather in the uniform corrosion for both types of specimens even though aluminium seemed to show more obvious. Adding trace amount of HCI or H[Subscript 2]S into the corrosive solution enhanced corrosion potential of dimethylmecury on metal remarkably, about 700 times higher than ones containing dimethylmercury solution without acid, and about 40 times higher than ones containing acid solution, but without dimethylmerury in the system. Especially in the case of aluminium specimens immersed in the dimethylmercury solution, the rate was rather frightening, 746 mg/sq. decimeter/day. The reason for this remarkable increase of the corrosion rate is that the acid molecule could break the bond between mercury and methyl group in the dimethylmecury to form inorganic salt which could then corrode metal easily, especially aluminium metal.