Chemical corrosion control for sour crude oil pipelines

Abstract

The effects of some amines as inhibitors for the corrosion of API-45 grade steel in NACE sour solution (5% NaCl and 0.5% CH3COOH solution saturated with H2S) have been investigated, using weight-loss, hydrogen-estimation, electrochemical and determination of tensile strength of materials techniques. The selection of amines chosen was made up of: ethanol amine (EA), triethyl amine (TEthA), dimethyl amine (DMA), diethyl amine (DEthA), triethanol amine (TFA), n-tributyl amine (TBA), cyclohexyl amine (CHA), dicyclohexyl amine (DCHA), pyridine (Py), ethylene diamine (EDA), furfuryl amine (FA), octyl amine (OA), and tri-iso octylamine (TIOA). It was found that TIOA affords the maximum protection to the metal under all the conditions tested. The inhibition efficiency of all the amines except that of TIOA decreased with rise in temperature from 25 to 70°C. Hydrogen absorption in the presence of inhibitors was considerably reduced; the rise in temperature brought down the hydrogen absorption by the steel. The inhibitors were found to affect both the anodic as well as the cathodic reactions. Effective inhibitors have retained the mechanical strength of steel to an appreciable extent, whereas in the absence and in the presence of inferior inhibitors, it is considerably reduced.