REASON ANALYSIS FOR CORROSION OF BUTTERFLY VALVES IN AMMONIUM SULFATE CRYSTAL SYSTEM

The parts for the butterfly valves were corroded,got black and broke off in short time after the butterfly valves was put into operation.Several methods including chemical composition analysis,microstructure examination,EDS analysis,contact corrosion experimentation and open circuit potential test were used to analyze the failure reason. The result showed that the general corrosion took place in the pins and shaft made from 304 steel in ammonium sulfate mother liquor. The second reason was the galvanic corrosion taking place between austenitic stainless steel of different chemical composition.