Abstract
The production of petrochemicals involves the handling, treatment and processing of hydrocarbons and organic chemicals, which are generally non-corrosive towards carbon and low alloy-steels, however these hydrocarbons can carry a number of impurities such as water, chlorides and acids that can generate corrosive conditions thereby compromising plant infrastructure. Therefore, in the petrochemical industry it is necessary to develop efficient and practical methods of corrosion control to maintain plant integrity.
An electrochemical high temperature and high pressure facility is used to study the corrosion behaviour of carbon steel 1018 in several petrochemical environments. The open circuit potential is measured and the effect of water and carboxylic acid concentration studied on the initiation of corrosion/fouling on carbon steel in a C6 solvent mixture at 220 ± 5° C. A corrosion mechanism is proposed that is similar to that previously proposed in the oil industry for naphthenic acid. As the concentration of total available H+ increases, through the addition of water or carboxylic acid the amount of general and localized corrosion on the carbon steel surface increases. Electrochemical impedance spectroscopy (EIS) is also used to analyze the change of impedance at the carbon steel/solution interface. Scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDX) are used to look at the nature of the deposits formed after two hours of open circuit measurement.
