Copper alloys have excellent resistance to atmospheric and seawater corrosion, such as silicon bronze, aluminum bronze and so on. In general media, it is dominated by uniform corrosion. There is strong stress corrosion susceptibility in the solution in the presence of ammonia, and there are also local corrosion forms such as galvanic corrosion, pitting corrosion, and abrasion corrosion. Dezincification of brass, dealumination of aluminum bronze, and denitrification of cupronickel are the unique forms of corrosion in copper alloys.
During the interaction of copper alloys with atmospheric and marine environments, passive or semi-passive protective films can be formed on the surface of copper alloys, which inhibits various corrosions. Therefore, most copper alloys show excellent corrosion resistance in atmospheric environments.
Atmospheric corrosion of copper alloys Atmospheric corrosion of metal materials mainly depends on the water vapor in the atmosphere and the water film on the surface of the material. The relative humidity of the atmosphere when the corrosion rate of the metal atmosphere begins to increase sharply is called the critical humidity. The critical humidity of copper alloys and many other metals is between 50% and 70%. The pollution in the atmosphere has a significant effect on the corrosion of copper alloys. The acidic pollutants such as C02, SO2, NO2 in the urban industrial atmosphere are dissolved in the water film and hydrolyzed, which makes the water film acidified and the protective film unstable. The decay of plants and the exhaust gas emitted by factories make ammonia and hydrogen sulfide gas exist in the atmosphere. Ammonia significantly accelerates the corrosion of copper and copper alloys, especially stress corrosion.
The corrosion susceptibility of copper and copper alloys in different atmospheric corrosion environments is quite different. Corrosion data in general marine, industrial and rural atmospheric environments have been reported for 16 to 20 years. Most copper alloys are uniformly corroded, and the corrosion rate is 0.1 to 2.5 μm/a. The corrosion rate of copper alloy in harsh industrial atmosphere and industrial marine atmosphere is an order of magnitude higher than that of mild marine atmosphere and rural atmosphere. Contaminated atmosphere can significantly increase the stress corrosion susceptibility of brass. Work is underway to predict and classify the rate of corrosion of copper alloys by different atmospheres based on environmental factors.
Post time: Jul-04-2022