Fundamental Corrosive Properties of Crude Oils and their Effect on the Ferrous Metals

Abstract

Crude oils are predominantly made of organic compounds foremost hydrocarbons, trace compounds and corrosive compounds as well. The interaction between crude oils and ferrous metals causes some severe ascendency on the ferrous metals due to the corrosive compounds in crude oils with the collaboration of the chemical compositions such ferrous metals. In this research it was expected to investigate the effect of both Murban and Das Blend crude oils on the corrosion rates of seven different types of ferrous metals. The contents of sulfur, mercaptans, organic acids and salts in both crude oils were determined by to XRF analyzer, titration methods and salt analyzer while testing the chemical composition of each metal by XRF detector. Batches of similar sized metal coupons were prepared from each type of metal and the corrosion rates of each metal coupon were determined by the weight loss method while after 15, 30 and 45 days from the immersed day while observing the corroded surfaces through the 400X lens of an optical microscope. The hardness of each metal coupon was tested by Vicker's hardness tester before immersion in the crude oil and after corroded. The concentrations of ferrous and copper were tested in each crude oil sample after exposed to the metals by the atomic absorption spectroscopy (AAS). There were found some higher corrosive strength in Das Blend than Murban although found higher corrosion rates from four types of metals in Murban than Das Blend and relatively lower corrosion rates in stainless steels than the other metals. Apart from that there were found significant concentrations of ferrous and copper in some crude oil samples especially regarding carbon steels and Monel. Also, slight reductions of the initial hardness were found from each metal coupon after the corrosion eventually.