Understanding the efficacy of concentrated interstitial carbon in enhancing the pitting corrosion resistance of stainless steel

By introducing a high fraction of interstitial carbon through low temperature carburization, the pitting corrosion resistance austenitic stainless steel can be significantly improved. Previous work attributed this to strengthening passive film by carbon. Here, however, we present paradigm shift showing that actually weakens but strengthens bonding within alloy forming localized (covalent) bonds with metal atoms (Fe, Cr, Ni). Accordingly, enhancement in is result reducing dissolution rate local pit environment many orders magnitude, which extremely decreases growth stability and prevents it from transitioning into stable growth. Electronic structure calculations confirm metal–carbon are 1.4 2.0 times stronger than metal–metal bonds. These results suggest new strategy for design resistant alloys, namely surface engineering infusion concentrated interstitials form strong matrix atoms.