Elevation of the Reliability of Corrosion Monitoring of Low-Carbon Steel in Tap Water

The negative influence of the localization of corrosion on the reliability of corrosion monitoring is analyzed for municipal water supply systems. We performed laboratory corrosion tests of St.3 mild steel in cold tap water and industrial corrosion tests in hot-water supply systems. By the methods of weight losses and polarization resistance, it is shown that the corrosion rate of St.3 mild steel remains constant and equal to 0.05 mm/yr in cold water and gradually reduces from 0.32 to 0.13 mm/yr in hot water in the tests carried out for 4500 h. The analysis of the distribution of corrosion defects on the surface of specimens after the corrosion testing showed that the general uniform corrosion is typical of cold tap water, whereas at elevated temperatures, the corrosion process becomes nonuniform. No local corrosion defects were found on the specimen surfaces under both laboratory and industrial conditions. Hence, no additional correction of the results of corrosion monitoring is required to take into account the phenomenon the local corrosion.