Fig. 4: Schematic of the mechanism of CP20-induced corrosion of mild steel (AH36).
From: Accelerated corrosion of marine-grade steel by a redox-active, cysteine-rich barnacle cement protein
a Cross section illustration of an adult barnacle, M. rosa, attached to a metal substrate; b Structure of CP20, redrawn from ref. 43; c CP20 diffuses proximally to the metal surface (on the left) and adsorbs strongly on the mild steel via its thiol functional groups (colored in red) and/or the positively charged patches on its surface (colored in blue). Redox-active disulfide bonds (colored in green) are also present in the vicinity of the adsorption site; and d CP20 drives metal–protein complexation, as shown in UV absorption studies, via the favorable redox reaction involving the reduction of disulfide bonds and oxidation of Fe, resulting in PIC. The autocatalytic nature of pitting accelerates the pitting corrosion at this site, accumulating corrosion products in the form of ferric or ferrous hydroxides. Inset: amino acid sequence for structure in b, with connected cysteine residues (C, in green) representing disulfide bonds.
