The corrosion behavior of corrosion-resistant alloys (CRA) in sour environments was investigated using a duplex stainless steel as a representative CRA. Changes in corrosion morphologies resulting from changes in environmental aggressiveness were elucidated. The application limits of CRA were shown to be determined by whether pitting corrosion occurred. A theory was proposed for predicting the corrosion morphologies and, thus, determining the application limits of the CRA. The validity of prediction by this new theory was confirmed by good agreement with results from long-term immersion tests and a field test for actual-size test pipes. Since this theory was based on the corrosion mechanism, it showed many advantages: The prediction was accurate, the results for one environment could be extended to other environments, and the prediction was conducted very quickly.

Subject
Noble potential, Sour environments, Aqueous environments, Aqueous solutions, Acidity, Corrosion attacks, Corrosion morphology, Steel, Pitting, Immersion, Alloys, Stress corrosion cracking, Types of corrosion
Keywords:
corrosion-resistant alloys, field testing, immersion testing, localized corrosion, morphology, oil and gas environments, pH, pitting corrosion, sour gas, stress corrosion cracking
NACE International
1995
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