What are the factors that cause copper alloy corrosion

Copper alloy corrosion

atmospheric corrosion
The 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 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 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.
splash zone corrosion
The corrosion behavior of copper alloys in the seawater splash zone is very close to that in the marine atmospheric zone. Any copper alloy that has good corrosion resistance to the harsh marine atmosphere will also have good corrosion resistance in the splash zone. The splash zone provides sufficient oxygen to accelerate corrosion of the steel, but makes it easier for copper and copper alloys to remain passive. The corrosion rate of copper alloys exposed to the spatter zone usually does not exceed 5 μm/a.
stress corrosion
Quaternary cracking of brass is a typical representative of stress corrosion of copper alloys. Seasonal cracks were discovered in the early 20th century and refer to the cracks in the part of the bullet casing where it shrinks toward the warhead. This phenomenon often occurs in the tropics, especially in the rainy season, so it is called seasonal cracking. Because it is related to ammonia or ammonia derivatives, it is also called ammonia cracking. In fact, the presence of oxygen and other oxidants, as well as the presence of water, are also important conditions for stress corrosion of brass. Other environments that can cause stress corrosion cracking of copper alloys include: atmosphere, fresh water, and sea water heavily polluted by SO2; sulfuric acid, nitric acid, steam, and aqueous solutions such as tartaric acid, acetic acid, and citric acid, ammonia and mercury used to clean parts.
Decomposition corrosion
Brass dezincification is a typical type of copper alloy de-composition corrosion, which can occur simultaneously with the stress corrosion process, or it can occur alone. There are two forms of dezincification: one is layered exfoliation type dezincification, which is in the form of uniform corrosion and is relatively less harmful to the use of materials; The strength of the material is significantly reduced, and the danger is greater.
Corrosion in marine environment
In addition to the marine atmospheric area, the corrosion of copper alloys in the marine environment also includes seawater splash area, tidal range area and total immersion area.