Study of localized corrosion of AISI 430 and AISI 304 batches having different roughness

In this work, the localized corrosion resistance of different batches of AISI 430 and AISI 304 stainless steels, having Scotch-Brite surface finishing, was investigated as a function of their roughness (in terms of Rz) and chemical composition. The study was performed by recording anodic cyclic potentiodynamic polarization curves at room temperature in two NaCl solutions (0.35 and 1.75 wt %). From the anodic curves, corrosion potential (E-corr), protection potential (E-prot), and pitting potential (E-pit) were obtained. In general, the results indicate that AISI 304 has better localized corrosion resistance than AISI 430, both in terms of pitting initiation and repassivation ability, independently from roughness. In particular, an increase of roughness determined a decrease of E-pit only in the case of AISI 304 in the less concentrated NaCl solution. This result was related to the higher variability of the corresponding Rz values compared to those of AISI 430. Finally, from the analysis of the loop hysteresis of the anodic curves, in relation to E-pit - E-prot values, durability information on the tested stainless steels were obtained: AISI 304 shows higher corrosion performances with respect to AISI 430, thanks to the higher chromium content of the former compared to the latter.