Copper alloy products in corrosive environments

Copper alloy has excellent corrosion resistance to atmosphere and sea water, and uniform corrosion is the main corrosion in general media. In ammonia containing solution, there is strong stress corrosion sensitivity, but also galvanic corrosion, pitting corrosion, wear corrosion and other local corrosion forms. Dezincification of brass, aluminium bronze and white copper are the special corrosion forms of copper alloys.

During the interaction between copper alloy and atmosphere and ocean environment, passive or semi-passive protective film can be formed on the surface of copper alloy to inhibit various corrosion. Therefore, most copper alloys exhibit 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 material surface. The relative humidity of the atmosphere at which the rate of metal corrosion begins to increase sharply is called the critical humidity, and the critical humidity for copper alloys and many other metals is between 50% and 70%. The corrosion of copper alloy is obviously enhanced by air pollution. Acidic pollutants such as CO2, SO2 and NO2 in the industrial atmosphere dissolve in the water film and hydrolyze, which acidifies the water film and destabilizes the protective film. Due to plant decay and industrial plant emissions, ammonia and hydrogen sulfide gas exist in the atmosphere, ammonia significantly accelerates the corrosion of copper and copper alloys, especially stress corrosion.

The corrosion sensitivity of copper and copper alloys varies greatly in different atmospheric corrosion environments. Corrosion data in general Marine, industrial and rural atmospheric environments have been reported for 16 to 20 years. Most copper alloys corrode uniformly, with corrosion rates ranging from 0.1 to 2.5 microns/year. The corrosion rate of copper alloys in harsh industrial and industrial Marine atmospheres is an order of magnitude higher than that in mild Marine and rural atmospheres. The stress corrosion susceptibility of brass is obviously increased by air pollution. Work is underway to predict and classify the corrosion rates of copper alloys in different atmospheres based on environmental factors.