Keywords: SCC, stress corrosion cracking, stainless steel, salt water, free machining, ambient temperature, failure analysis, sulphur content, marine environments, corrosion resistance, North Sea offshore platforms, oil platforms, microstructure, forging, hydrogen sulphide, platform decks, airborne salts, ocean spray, forged steel fasteners
Failure analysis showing the effect of sulphur content in stainless steel on the resistance to stress corrosion cracking in marine environments at ambient temperatures
The risk of environmentally assisted cracking in downhole components is high due to sour conditions, i.e. the presence of hydrogen sulphide. Therefore a range of materials possessing excellent corrosion resistance are employed. However, corrosion is not only downhole related but is also a common problem on the platform deck itself due to airborne salts from ocean spray. For this reason the platform deck and the splash zone at the waterline are considered harsh marine environments. Commonly, stainless steels are selected to provide increased corrosion resistance. This study demonstrated that sulphur content and microstructure can affect the corrosion resistance of stainless steel in marine environments at ambient temperatures. Stress corrosion cracking was observed below the threshold of 50°C on actual components from the field and in marine–type environment laboratory corrosion tests. The laboratory testing thus validated the improved corrosion resistance of forged 304 stainless steel fasteners over machined 303 stainless steel.