Jet-in-Slit Test for Reproducing Flow-Induced Localized Corrosion on Copper Alloys

Valve seat rings of water taps made of copper alloys occasionally suffer corrosion damage as a result of water quality and fluid flow. Examination of the damage mechanisms and development of a testing method for selecting durable materials were requested. To solve these problems, 10 copper alloys were examined using three test methods under accelerated, but well-known experimental conditions: the ISO 6509 dezincification test for pure corrosion, the vibratory cavitation test with eccentric stationary specimen for cavitation erosion-corrosion, and the jet-in-slit test for flow-induced localized corrosion. The alloys were ranked in order of merit. Rankings obtained in the jet-in-slit test agreed with rankings determined by experiences of field engineers who have dealt with these problems under practical conditions. It was concluded that damage on the valve seats was caused by flow-induced localized corrosion. The jet-in-slit test was recommended as a reliable method in selecting durable valve seat materials. To explain the excellent coincidence with field performance in the jet-in-slit test, the mechanism of corrosion rate acceleration, characteristics of flow-induced localized corrosion, and composition of the protective corrosion products layer were investigated. Under the test conditions, the corrosion reaction mechanism was found to be the same as in the field, but the corrosion rate was accelerated.