Investigation of localized corrosion resistance of type 441 stainless steel annealed at different temperatures by means of a metastable pitting analysis

The localized corrosion resistance properties of type 441 stainless steel used in the manufacturing of boiler heat exchangers were investigated by means of metastable pitting events analysis, observed in the cyclic potentiodynamic anodic curves. The experimentation was carried out on specimens obtained from not annealed and in-line annealed pipes at 700 and 900 °C. The Cyclic Potentiodynamic Polarization tests were conducted in neutral NaCl solutions characterized by chloride concentrations of 125 and 500 ppm. The results obtained from the analysis of the characteristic potentials and the metastable pitting events, determined from the experimental curves, showed that the localized corrosion resistance performances of type 441 stainless steel are higher after the annealing at 900 °C if compared to that at 700 °C.