The electrochemical behavior and corrosion of carbon steel in various types of naphthenic acid solutions have been studied by using cyclic voltammetry technique. The data reveal that the anodic excursion spans of carbon steel in naphthenic acid solution are characterized by the occurrence of a well-defined anodic peak (peak A), followed by a passive region. The passivation may be related to the formation and precipitation of oxide film on the electrode surface. The data reveal that increasing naphthenic acid concentration enhances the anodic peak current density (I-pA) and shifts its peak potential towards more positive values. The corrosion rate of carbon steel depended critically on the naphthenic acid types. The rate of the corrosion process increased with increasing in molar mass of naphthenic acid, reaching a maximum value in the presence of CHPA acid (C-9), and then decreased.Potentiodynamic polarization measurements indicated that ethoxylated fatty acid derivatives have a strong effect on the corrosion behavior of the carbon steel in naphthenic acid solutions. The inhibition efficiency of these compounds was found to vary with their nature and concentration. The order of effectiveness of the inhibitors was OL(EO)(80) > OL(EO)(40) > OL(EO)(20). The adsorption of ethoxylated fatty acid on the carbon steel surface in naphthenic acid solutions was found to obey Frumkin isotherm and kinetic-thermodynamic model. (C) 2007 Elsevier Ltd. All rights reserved.

Corrosion in atmospheric distillation is caused by hydrochloric acid produced by the hydrolysis of water soluble magnesium and calcium chlorides found in the crude oil. Corrosion of copper metal during distillation of Geisum crude oil (vapour phase ) at 100, 150, 200, 250, and 300°C in absence and presence of 5 per cent H 2 O was studied. The corrosion of copper metal in the vapour phase is higher than in the liquid phase. Hydrogen sulphide is not the only corrodant present; hydrogen chloride and volatile acids are other important corrodants. The effect of adding different inhibitors with various concentrations on the corrosion of copper metal was also studied. The rate of inhibition increases with addition of chlorinated hexadecylamine as compared with that obtained by addition of ammonia alone. The inhibitive efficiency of copper increased rapidly as the copper benzotriazole film grows rapidly.

The distillation unit separates the crude oil into various boiling range fractions. These fractions are further refined into finished products. The paper deals with the corrosion of C-steel metal during distillation of Gysume crude oil (vapour phase) at 100-degrees, 150-degrees, 200-degrees, 250-degrees and 300-degrees-C in absence and presence of 5% H2O. The effect of adding different inhibitors with various concentration on the corrosion of C-steel metal are studied.

The saturated hydrocarbon fraction separated from lube oil distillate was blended with different sulphur compounds: aliphatic sulphide, mercaptans, thiophenes and aromatic sulphide at different concentrations. The effect of addition of different concentrations of sulphur compounds on the oxidation stability of the lube oil was studied using standard method in IP. DTA and thermogravimetric techniques. Antioxidants zinc dialkyldithio phospate and succinimide were added to improve antioxidant properties and their effect was studied using thermogravimetric technique. It was found that sulphur compounds play an important role in the stability of lube oil.