Effect of testing temperature on corrosion behaviour of different heat treated stainless steels in the active-passive region

Purpose - This paper aims to focus on the effects of temperature of the immersion media on the corrosion behaviour of differently heat-treated X20Cr13 stainless steel. Design/methodology/approach - Specimens, quenched on air, quenched in oil and quenched in oil and then tempered, were tested during exposure in 0.1 M H2SO4 at 30, 40 and 50 degrees C. The results were interpreted on the base of potentiodynamic and impedance measurements. Findings - From the impedance spectra a reaction mechanism can be determined: after samples had reached and passed the active peak, expressed as the highest peak on the potentiodynamic curve, corrosion products at interfaces, which were adsorbed at metal surface, led to an increase in the charge transfer resistance. Elevated temperature of immersion media has had appreciable influence on the corrosion rate and adsorption of products, but at this temperature level did not affect the principle of corrosion reactions. Activation energies were calculated to exhibit temperature dependence of current density which was the highest for the oil- and the lowest for the air-quenched sample. Originality/value - The paper provides further research on stainless steel, the corrosion behaviour of which can be controlled already by heat treatment.