THE EFFECT OF SOLUTION ANNEALING ON THE CORROSION RESISTANCE OF A WELDED 0.36%C STEEL IN CHLORIDE ENVIRONMENT

Carbon steel is fundamentally an alloy comprising of iron and carbon, and other alloying elements such as manganese with 1.0% maximum content and silicon with 0.3% maximum content (Onyekpe, 2002). It is the most important steel used in petroleum and chemical industries since it accounts for over 98% of the construction materials. Carbon steels materials are predominantly used for flow lines, transmission pipelines and downhole tubulars in the oil and gas industry, most possibly owing to their low cost (Nesic et al, 2010; Ghareba et al, 2010; Liu et al, 2011; Badr, 2009). For instance, the cost of stainless steels especially that of austenitic steels (AISI 304 & 316) is currently about 8 times greater than that of carbon steels (Panossian et al, 2012; Finsgar et al, 2014). Among the most widely used carbon steel is the medium carbon steel. It is classified on the basis of their carbon content varying from 0.25% to 0.5%. The carbon steel that has been mostly used as the main production material for transmission pipelines, downhole tubulars, and flow lines in the oil and gas industry is API N80 (Walker, 1994; Yadav et al, 2012; Vishwanatham et al, 2008; Zhu et al, 2011), with carbon varying from 0.23% - 0.52%, (Finsgar et al, 2014). However, this material is susceptible to corrosion when used in chloride environment without any form of surface treatment or protection (Seidu and Ketulu, 2013).