Corrosion in Aqueous Solution of Two Alkanolamines with CO₂ and H₂S: <i>N</i>-Methyldiethanolamine + Diethanolamine at 393 K

Abstract

In this work we have used an apparatus constructed in our laboratory to systematically study the corrosion rate on metals and evaluate specialty chemical products for preventing metal corrosion in industrial plants. We performed experimental studies on the effect of specific variables on corrosion rates over carbon steel, such as pressure, concentration of alkanolamines in aqueous solution, and amount of acid gases (CO 2 and H 2 S). The technique utilized to evaluate the corrosion rate is the well-known weight loss method. With the experimental apparatus and method developed in this work we have determined the corrosion rate of AISI 1010 carbon steel in aqueous solutions of known concentration of N -methyldiethanolamine (MDEA) and diethanolamine (DEA), individually, with and without acid gases, and in different alkanolamine blends with total alkanolamine mass fraction in the range 15−60%, with mass ratios of MDEA/DEA of 3.5/1 and 2/1, with the addition of different amounts of H 2 S and CO 2 at a pressure range of 276−5861 kPa (40−850 psig). Corrosion rates over carbon steel were determined in the liquid phase and also in some runs in both liquid and vapor phases, at 393.15 K. In the studied systems the corrosion rate decreases when the concentration of the alkanolamine increases. It was also possible to establish the effect of the amount of CO 2 and H 2 S, in an individual way as well as in a mixture, on the corrosion rate of the carbon steel. The results show that corrosion rate of the alkanolamine solutions is not affected by CO 2 in the range 0−0.35 mol; however, the presence of H 2 S drastically increases the corrosion rate as the amount of H 2 S increases.