Comparison of current reversal chronopotentiometry (CRC) and small amplitude cyclic voltammetry (SAC) method to determine the long-term corrosion tendency of copper- nickel alloys in polluted and unpolluted seawater under jet-impingement conditions

摘要

The cyclic current reversal chronopotentiometry (CRC) technique is utilized to determine the long-term corrosion tendency of UNS C70600 and UNS C71500 copper-nickel alloys in sulfide polluted and unpolluted sewater. The CRC results were compared with the corrosion tendency obtained by the modified linear polarization method Small Amplitude Cyclic Voltammetry (SACV) over a long exposure time and the results are in agreement for both C70600 and C71500 alloys. This contradicts the conclusions on the effects of sulfide on copper-nickel alloys by many previous investigators who misinterpreted the sharp active shift in potential as an indication of increase in corrosion rate. For an active/passive alloy such as C71500 a higher amplitude current per cycle is required (e.g. 100 muA/20 seconds) in the CRC method and under jet-impingement conditions, while a lower amplitude current per cycle (e.g. 1muA/20 seconds) is required for an alloy that does not exhibit active/passive behavior. The CRC technique was found to be unsuccessful in screening out the long-term corrosion tendency of copper alloys in polluted and unpolluted sea water and under stagnant or stirred conditions (i. e. non-jet impingement conditions).