A Comparison of Vertical Electro-Gas Welding and Submerged arc Welding Methods on the Corrosion Behaviors of Crude Oil Storage Tank Steel in Simulated Seawater

Abstract

Large crude oil storage tanks (LCOSTs) are generally fabricated by high strength low alloy (HSLA) steels via welding process. In this paper, a comparison of vertical electro-gas welding (VEGW) and submerged arc welding (SAW) methods on the corrosion behaviors of HSLA steels in simulated seawater has been investigated by open circuit potential (OCP) monitoring, potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS) measurement. Results reveal that the welding process would decrease the corrosion resistance of HSLA steel, and the VEGW joint shows better corrosion resistance than SAW joint, due to the nobler OCP values, decreased corrosion current density, lesser impedance value (|Z|) and smaller weight loss. The corrosion products formed on the surface VEGW joint are more compact than SAW joint, which can account for the fact that the VEGW joint owns better corrosion resistance than SAW joint.