The effect of hypochlorite treatment on stainless steel performance and fouling in cooling water cycles

Water-cooling using natural waters is typically utilized for cooling large industrial facilities such as power plants. Cooling systems using natural water are susceptible to biofouling, which refers to the undesirable accumulation of biotic deposits on a surface. In the industrial systems, the biofouling together with inorganic fouling and scaling can cause problems such as an increase in the flow resistance of pipelines or a decrease in the thermal transfer capacity of the heat exchangers, and corrosion. Chemical cleaning of the affected area, for example hypochlorite treatment, is the main method used for removing unwanted biofilms in the cooling water systems. The corrosion behaviour of two stainless steels (AISI 316, SMO 254) in the cooling water cycle of a power plant using hypochlorite as an antifouling biocide and the efficiency of the hypochlorite treatment against fouling were studied here. The corrosion rate and biofouling were monitored during the three- month experiment period by using LPR-technique and a commercial biofouling-probe. The chlorination pulse increased momentarily the corrosion rate of both stainless steels. The detected corrosion rates were so low that visible corrosion could not be detected within the experiment time. The used chlorination dose proved to be efficient against biofouling during the experiment period. The results highlight the importance of the optimization of usage of the biocides in both materials performance and biofouling prevention