Corrosion Causes of Industrial Water Pipes under Reclaimed Water Environment in a Power Plant

Leakage occurred in the operation of industrial water pipes in a power plant. X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy (SEM) were used to analyze the surface and inner layer corrosion morphology and corrosion product composition of the pipe. The total numbers of colony forming unit (CFU) of heterotrophic bacteria, sulfate reducing bacteria (SRB) and iron bacteria (IB) in circulating water system were detected by maximum probable number (MPN) method. The residual chlorine mass concentration in the system was detected by residual chlorine analyzer. The results show that total heterotrophic bacteria beyond the prescribed standards, SRB and IB were detected in many sampling points in the system. The residual chlorine consumption at 0.5 h after the addition of bactericide accounted for more than 50% of the residual chlorine consumption at 8 h. The bactericidal effect under the method of regular dosing of bactericide did not meet the standard requirements. Microorganisms were involved in corrosion, forming a large number of rusts and attachments on the inner wall of the pipeline. Cl^- was enriched under the attachments, and autocatalytic corrosion occurred, which aggravated the dissolution of the metal matrix and eventually led to pipeline leakage.