Comparative study on the inhibition of copper oxide, nickel, and sodium tungstate on microbially induced concrete corrosion under sewer conditions
Microbially induced concrete corrosion (MICC) is a significant issue that reduces the service life of sewer systems. Bacteriostatic agent in concrete can inhibit microbial activity and the process of MICC to some extent. However, a systematic comparison of the inhibition effects of various bacteriostatic agents on MICC remains lacking. In this study, three bacteriostatic agents (copper oxide, nickel, and sodium tungstate) were investigated for their inhibitory effects on MICC. For each inhibitor, the cement mortar coupons with 0.05 wt%, 0.1 wt%, and 0.2 wt% of the inhibitor were prepared. The coupons were partially submerged in sewage of a controlled laboratory corrosion chamber (20 {+/-} 5 ppm H2S) to simulate the tidal region of gravity sewer. During the 56 days of exposure, the intensification of pores, cracks, surface erosion, and spalling was observed on all coupons. After 56 days of exposure, the sulfate concentration and adenosine triphosphate (ATP) content of coupons without inhibitor were 10.65 mg/cm2 and 30.17 {+/-} 3.87 mol/cm2, respectively. They were higher than those of coupons containing 0.05 wt%, 0.1 wt%, and 0.2 wt% of copper oxide and 0.05wt% of nickel. The temporal profiles of ATP of coupons without inhibitor was similar to those of coupons containing sodium tungstate. After exposure for 28 days, the surface pH of coupons without inhibitor was 7.45, meanwhile of those coupons containing 0.2 wt% of copper oxide and 0.05 wt% of nickel were 9.42 and 9.93, respectively. Those results indicated that the bacteriostatic effect of copper oxide and nickel (0.05 wt %) was found to be the most prominent. The findings indicate that a single bacteriostatic agent is only effective during specific corrosion stages, suggesting that a combination of multiple agents may be a promising strategy to combat the multi-stage MICC process over the long term. This study provides a theoretical basis for the selection and development of protective materials against concrete corrosion in sewer networks.