Influence of Si nanoparticles on the electrochemical behavior of organic coatings on carbon steel in chloride environment

Scanning electrochemical microscopy (SECM) is an excellent technique to detect electrochemical processes with high spatial resolution. In this work, the effect of silicon (Si) nanoparticles on the corrosion protection performance of epoxy-coated steel was examined by electrochemical impedance spectroscopy (EIS) and SECM analysis. The EIS was performed in continuous immersion in 0.1 M NaCl_(aq) solution. The addition of Si nanoparticles increased the coating film resistance (R _f) and the charge transfer resistance (R _ct) of coated steel. SECM mapping and line scan analysis was performed in order to estimate the coating performance with Si nanoparticles in 0.1 M NaCl_(aq) solution. SECM results indicated that the tip current at -0.70 V was decreased by the addition of Si nanoparticles in epoxy film. These results suggested that the dissolved oxygen (DO) was consumed by anodic dissolution of Si nanoparticles. Surface analysis showed that the Si was enriched at the scratched region of the coated steel after a corrosion test. From these results, Si was dissolved as Si ⁿ⁺ and transferred to the scratched area, and then consumed the DO in the solution. Thus, the anodic dissolution of Fe at the scratched area was suppressed by the Si nanoparticles, which implies the sacrificial effect of Si from the coating against the steel corrosion. Hence, it was concluded that the Si nanoparticles had a beneficial effect on enhancing the corrosion resistance of the coated steel.