INFLUENCE OF Ni ADDITION ON CORROSION BEHAVIOR OF STEELS FOR DEEPWATER APPLICATIONS

摘要

The interest in the use of high grade steel pipes for the construction of long distance pipelines is rapidly increasing, and is expected to become the main driving force for deepwater steel investigations. In response to this potential demand, the steel makers are making strong efforts to develop new grades of steel. In the present work, an ultra high-strength steel grade that far exceeds the conventional grades X65 and X80 has been studied to investigate the influence of minor alloying additions of nickel on the microstructural pattern and the corrosion resistance behavior. Nickel is commonly used to raise the strength of the steel. This kind of steel can exhibit different corrosion responses due to nickel content and the resulting differences in microstructural features. Electrochemical experiments further showed that nickel addition was detrimental to the corrosion resistance. The increase of nickel content has provided a microstructure refinement and a more extensive redistribution of the precipitation which has provoked a decrease on the corrosion resistance.