The Strength of Corrosive Properties of Crude Oils on Ferrous Metals

Crude oil is an unrivaled earth resource for the most of industrial applications. In the refining process of crude oil, ferrous metals play a severe role against the harsh environment while confronting adverse influences of crude oils such as the corrosion of ferrous metals. The formation of metal oxides, sulfides, hydroxides or any compound related with carboxylic group on the metal surface is known as the corrosion also mainly depends on the sulfur content, acidity, salt content and mercaptans content of relevant crude oils as well as the chemical composition of the metal. In this research it was expected to speculate the effect of such corrosive properties of Murban and Das Blend crude oils on seven different types of ferrous metals which are used in crude oil refining industry of Sri Lanka. The sulfur content, salt content, acidity and mercaptans content of each crude oil were determined by the succession of XRF analyzer, analyzer of salt and titration methods. A range of similar sized pieces of seven different types of ferrous metals were immersed in both crude oils separately and their corrosion rates were determined after 15, 30 and 45 days from the immersion by the weight loss method while observing the corroded metal surfaces under the optical microscope. The metallic concentrations in both crude oil samples after the experiment were tested by the AAS. It was found that the higher content of sulfur, acidity, mercaptans and lower content of salt in the Das blend than the Murban. According to the corrosion rates of metals, four types of metals showed higher rate of corrosion in Murban while other metals are showing higher corrosion rate in Das blend also higher metallic concentrations were obtained from Murban crude oil samples than Das Blend crude oil samples in the analysis of the AAS