Sensing Stress Corrosion Cracking in Phosphorus Copper Tubes

The leakage of fluorocarbon refrigerants due to corrosion of phosphorus copper tubes, which are widely used in air conditioners, is a growing environmental threat. In this study, to prevent this leakage, which is caused by stress corrosion cracking, we attempted to detect corrosion using a sensor that comprises a galvanic couple consisting of the copper tube and a carbon electrode. On testing in the presence of ammonia, the sensor detected a rise in background current, revealing the formation of a water film in which ammonia gas dissolves, with current noise identifying localized corrosion and oscillation of the background current indicating gas leakage. These phenomena can be detected by simply monitoring the current.