Introduction to the corrosion products of copper:
Corrosion products in air
When copper is slowly oxidized in air, copper green will be formed, whose main component is alkaline copper carbonate (Cu₂(OH)₂CO₃), and its color is green. This is one of the most common corrosion products of copper, and this green color will gradually appear on the surface of copper in humid air.
In sulfur-containing environments corrosion products
If copper is in a sulfur-containing environment, black copper sulfide (CuS) may be produced. Copper sulfide is usually produced when copper comes into contact with sulfur-containing substances such as hydrogen sulfide.
Corrosives in chlorinated environments
In chlorine-containing environments, copper can corrode to form green copper chloride (CuCl₂). CuCl₂ also sometimes appears as a blue-green color, depending on its concentration and the form in which it is present. In addition, under different corrosion conditions, copper corrosion products may have other colors and compositions, such as in some complex environments may appear brown, blue and other different colors of corrosion products.
How to improve the corrosion resistance of copper?
First, take the surface treatment
Passivation treatment: the use of chemical methods in the formation of a dense layer of passivation film on the surface of copper, this film can prevent oxygen, moisture and other corrosive media and copper surface contact, thereby improving corrosion resistance. For example, the use of chromate, benzotriazole and other passivators for processing, can effectively enhance the corrosion resistance of copper in the atmosphere.
Electroplating or chemical plating: A layer of corrosion-resistant metal or alloy, such as nickel, chromium, zinc, etc., can be plated on the surface of copper. These plating layers can play the role of physical barrier to prevent corrosive media erosion of copper.
Nickel plating improves the corrosion resistance of copper in wet environments, while chromium plating gives copper better abrasion and corrosion resistance. Chemical nickel-phosphorus plating also provides good corrosion protection for copper.
Organic coating: An organic coating, such as epoxy resin, polyurethane, etc., is applied to the surface of copper. The organic coating can isolate the corrosive medium and also play a decorative role. For some copper products used in indoor or mildly corrosive environments, such as decorations, electrical shells, etc., the use of organic coatings is a simple and effective anti-corrosion method.
Second, take alloying or micro-alloying
Add alloying elements: add some alloying elements in copper, such as tin, aluminum, nickel, etc., can change the organizational structure of copper, improve its corrosion resistance.
For example, tin bronze is an alloy formed by adding tin elements in copper, which has good corrosion resistance and mechanical properties, and is widely used in shipping, chemical industry and other fields.
Aluminum bronze, on the other hand, adds aluminum elements to copper, which has higher strength and corrosion resistance.
Micro-alloying, on the other hand, is by adding trace alloying elements, such as boron, zirconium, titanium, etc., which can refine the grain of copper and improve its corrosion resistance. These trace elements can form stable compounds at the grain boundaries of copper, preventing the diffusion of corrosive media. For example, trace boron can significantly improve the corrosion resistance of copper violet in seawater.
Third, environmental control
Reduce humidity, in the storage or use of copper products in the environment, reduce humidity can effectively reduce the occurrence of corrosion. You can use dehumidification equipment, desiccant and other methods to control the environmental humidity. For some humidity-sensitive occasions, such as electronic equipment, precision instruments, etc., to maintain a low humidity environment to improve the corrosion resistance of copper violet is crucial.
Avoid contact with corrosive media. When using copper violet products, try to avoid its contact with corrosive media, such as acid, alkali, salt solutions. If it is impossible to avoid contact, protective measures can be taken, such as the use of corrosion-resistant packaging materials, coatings and so on. For example, when transporting copper products, you can use plastic film, foam and other packaging materials for protection to avoid contact with external corrosive media.
Fourth, pay attention to maintenance
Clean the surface, regular cleaning of copper products, remove surface dirt, dust and other impurities, can reduce the occurrence of corrosion. You can use mild detergent and soft cloth for cleaning, avoid using corrosive cleaning agents.
Also note that the surface condition of copper products is checked regularly, and corroded parts are found and repaired in time. For minor corrosion, sandpaper sanding and polishing can be used to repair; for serious corrosion, professional repair or replacement may be required.
For example, in the chemical equipment used in the purple copper piping, regular inspection and repair can ensure the safe operation of the equipment, to avoid the occurrence of leakage and other accidents caused by corrosion.
