Effect of tempering temperature and microstructure on the corrosion behavior of a tempered steel

In this study, a tempered martensitic matrix was obtained in a low carbon steel, by applying austenization, quenching and tempering heat treatments. After austenization at 1000A degrees C for 30 minutes, steel samples were quenched in water and then tempered at 200, 540 and 600A degrees C for 30 minutes. Hardness measurements were done and then immersion tests were carried out in a 3.5 wt % NaCl solution for periods ranging between 1-7 days. Weight losses of the samples were determined after each immersion period and microstructural studies were performed on the corroded surfaces. Corrosion rates were calculated using weight loss data and verified by potentiodynamic tests. Results revealed that corrosion behavior of the experimental steels was directly affected by tempering temperature, hardness and microstructure.