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.
Keywords: High-strength steel grade, Nickel additions, Carbonitride precipitation,
Microstructural characterization, Corrosion behavior.