Corrosion behaviors of a Cr-Si alloyed anti-oxidation press-hardened steel in 3.5 wt.% NaCl solution

This study investigates the corrosion behavior of a Cr-Si alloyed anti-oxidation press-hardened steel (PHS) in a 3.5 wt.% NaCl solution through comprehensive microstructural characterization and potentiodynamic polarization measurements, with comparisons made to conventional 22MnB5 steel. The corrosion characteristics of the two steels differ markedly. The elevated Cr content in the Cr-Si alloyed PHS promotes the formation of a passive film during corrosion, which suppresses the corrosion rate. However, the precipitation of Cr-rich carbides in the matrix induces localized Cr- and C-depleted zones adjacent to these carbides, leading to a corrosion mechanism dominated by pitting. Increasing the austenitizing temperature facilitates the dissolution of Cr-rich carbides, homogenizes the elemental distribution in the matrix, and consequently lowers the susceptibility to pitting, thereby enhancing the corrosion resistance of the PHS. In contrast, the fully martensitic microstructure of 22MnB5 steel not only exhibits pitting corrosion but also contains high-energy martensitic lath boundaries that serve as preferential corrosion sites, resulting in comparatively inferior corrosion resistance relative to the Cr-Si alloyed PHS.