CORROSION PERFORMANCE AND APPLICATION LIMITS OF CORROSION-RESISTANT ALLOYS IN OIL-FIELD SERVICE

The corrosion behavior of corrosion-resistant alloys (CRA) in sour env ironments was investigated using a duplex stainless steel as a represe ntative CRA. Changes in corrosion morphologies resulting from changes in environmental aggressiveness were elucidated. The application limit s of CRA were shown to be determined by whether pitting corrosion occu rred. 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-si ze test pipes. Since this theory was based on the corrosion mechanism, it showed many advantages: The prediction was accurate, the results f or one environment could be extended to other environments, and the pr ediction was conducted very quickly.