The Influence of NaClO on the Biocorrosion of Carbon Steel Induced by Chlorella vulgaris in Artificial Seawater

Microbiologically influenced corrosion (MIC) poses a significant threat to carbon steel facilities in marine environments. Due to its environmental friendliness and excellent bactericidal effect, NaClO has been widely applied in the marine industry to inhibit MIC. In fact, algae can also cause severe biocorrosion to carbon steels. However, there are very few studies on the biocorrosion induced by algae, and thus the algicidal effect of bactericide NaClO is still unclear. In this study, the biocorrosion of 45# mild steel induced by Chlorella vulgaris (C. vulgaris) and the effect of NaClO on the biocorrosion were systematically investigated. The results showed that the corrosion rate of the steel in C. vulgaris-containing biotic artificial seawater was significantly higher than that in the abiotic solution. An increase in NaClO concentration resulted in a higher corrosion rate of the steel in general but relatively mild local corrosion penetration. The overall corrosion damage of the steel in the biofilm-covered areas was alleviated, while the corrosion penetration in the biofilm-discontinuous area became deeper after NaClO addition. The addition of 1 ppm NaClO into the biotic artificial seawater could not significantly inhibit the growth of C. vulgaris. When NaClO concentration increased to 10 ppm, the growth of C. vulgaris was markedly suppressed, resulting in a lower corrosion rate than that at 0 ppm and 1 ppm NaClO. At 100 ppm of NaClO, C. vulgaris cells were completely killed, and the overall corrosion rate in the biotic solution was close to that in the abiotic solution. Based on the experimental observations, algae-induced corrosion and its inhibition by NaClO were finally analyzed.