Study On Corrosion Mechanism Of NSE36 Steel Wire And Joint

The corrosion environment in cargo oil tanks (COT) is very complex. There are two types of corrosion in cargo oil tank, the general corrosion with flaky corrosion products at upper deck plate and pitting (localized) corrosion at inner bottom plate. Coating has been applied to conventional steel for the purpose of the corrosion prevention. However, the localized corrosion may occur in area of broken coating. Using corrosion resistant steel is an alternative means of corrosion prevention for cargo oil tanks and the standard was approved by International Maritime Organization (IMO). At present, only Japan can produce corrosion resistant steel. This situation may have cause great negative influence on our industry such as shipbuilding, steelmaking, transportation, etc. So it is necessary to develop corrosion resistant steel and welding wire for our county.Comparison experiments were conducted on the weld joint between newly developed wires in terms of mechanical properties and corrosion resistant properties. The mechanical properties of joint with newly developed wire are good. Weld metal and base material are active in10%NaCl acid solution (pH=0.85) which simulates corrosion environment of the bottom plates. The newly developed wire is alloy wire and its corrosion resistance shows perfect match with base material. Surface of weld metal with the newly developed wire is smooth and no large pitting hole, and there are a few particles which is rich in copper in weld metal.Weld metal thermodynamic stability, free corrosion potential, general corrosion resistance and pitting corrosion resistance can be inproved by the element Ni. Cu can improve weld metal corrosion resistance and suppress the formation of Fe3O4corrosion product.