The role of non-metallic Al2O3 inclusions, heat treatments and microstructure on the corrosion resistance of an API 5L X42 steel

The role of heat treatments, non-metallic aluminium oxide inclusions, and microstructure on the corrosion resistance of an API 5L X42 steel was examined in a 0.1M chloride environment (pH∼7). Energy Disperse Spectrometry analysis found aluminium oxide inclusions on as-rolled, annealed, normalised, quenched, and quenched plus tempered samples. Heat treatments changed the percentage of aluminium oxide inclusions in X42 steel. Annealed, normalised, quenched, and quenched plus tempered samples reached mean values of 0.15, 0.15, 0.12 and 0.07 percent respectively, whereas, rolled samples reached a mean value of 0.85 percent. It was found that the percentage of aluminium oxides did not affect the corrosion rate but promoted pitting corrosion. The average corrosion rate showed the following order in millimetres per year: as-rolled (0.067)