Synergistic adsorption and corrosion inhibition of nano carbon dots and random chitosan chains in 15 % HCl

The synergistic adsorption of carbon dot and chitosan on metal-corrosive solution interface remains complex and elusive due to their distinct architecture and chemistry. Here, copper-doped carbon dot (CuCD) and pyridine-grafted chitosan (CS-4PCA) are designed as a synergistic corrosion inhibition duo in 15 % HCl. Weight loss tests showed that the optimal CuCD (200 mg/L) and CS-4PCA (200 mg/L) individually achieved inhibition efficiencies of 67.66 % and 73.27 %, respectively. Remarkably, their binary mixture (150 mg/L CuCD + 50 mg/L CS-4PCA) exhibited a synergistic efficiency of 83.27 %, surpassing the performance of either component at the same total concentration. The addition of benzotriazole (200 mg/L) further enhanced the efficiency to 92 %. Surface characterization revealed that the CuCD/CS-4PCA composite film reduced the surface roughness of N80 steel from 32.27 μm (blank) to 8.01 μm, forming a compact protective layer. Molecular dynamics simulations demonstrated that CuCD adsorbed parallel to the Fe surface, while CS-4PCA chains filled the gaps, synergistically inhibiting corrosive particle penetration. This work provides insights into the design of high-performance compound inhibitors for harsh acidic environments.