Basics of the Metallic Corrosion in Crude Oils

Corrosion is an often-used term regarding the ferrous metals also the general phenomenon of the formation of metal oxides, sulfides, hydroxides or any certain compound on the metal surface itself. There were found the effect of corrosive compounds in crude oils on the metallic corrosion in most of researches up to certain stage. In the current research it was expected to speculate the effect of sulfur, mercaptans, organic acids and salts in both Murban and Das Blend crude oils on the corrosion rates of seven different types of ferrous metals and variations of the hardness of such metals. The corrosive properties of both crude oils were determined by the standard methods and instruments. The chemical compositions of metals were detected by XRF detector. A batch of similar sized metal coupons was prepared, and those metal coupons were immersed in both crude oils separately. The rates of corrosion of those metal coupons were determined by the weight loss method after 15, 30 and 45 days from the immersion also both initial hardness and hardness after corroded of each metal coupon were tested by Vicker’s hardness tester. The corroded surfaces were observed by the optical microscope also the ferrous concentration and copper concentration of each crude oil sample were measured by the atomic absorption spectroscopy (AAS) after exposed to metals. There were found relatively lower corrosion rates from stainless steels than other metals, higher corrosion rates of four types of metals in Murban crude oil although it was composed lower amount of sulfur, mercaptans, organic acids and higher amount of salts than Das Blend, higher ferrous concentrations in crude oil samples which were exposed to carbon steels than other crude oil samples whereas high concentrations of copper in crude oil samples relevant to the Monel metal and eventually it was a slight reduction of the initial hardness of each metal coupon due to the corrosion.