TEMPERING EFFECT ON THE LOCALIZED CORROSION OF THE 13CR4NI0.02C AND 13CR1NI0.15C STEELS IN A SYNTHETIC MARINE ENVIRONMENT

Primarily, tempering is used in martensitic stainless steels with low carbon in order to change their mechanical properties. However, it also modifies the corrosion properties; usually depending on the temperature and duration of the heat treatment. This work investigated the impact of tempering on the corrosion of 13Cr4Ni0.02C and 13Cr1Ni0.15C (% weight) steels. Samples were tempered at 650º, 700º and 750ºC, characterized by optical microscopy and cyclic anodic polarization tests in a synthetic marine environment. The results showed differences in the microstructure of the 13Cr4Ni0.02C tempered samples, which changed from lath to lamellar with precipitates in the prior austenite grain boundaries. On the other hand, tempering did not affect the 13Cr1Ni0.15C microstructure. The anodic polarization tests showed that the pitting potential of the 13Cr4Ni0.02C samples decreased with the tempering temperature increasing. Similar values of pitting potential were found with the 13Cr1Ni0.15C tempered samples, which were lower than the 13Cr4Ni0.02C samples after tempering. It shows that even though the corrosion resistance of the 13Cr4Ni0.02C reduces when the tempering temperature was increased, it is better than that presented by 13Cr1Ni0.15C.