Why does it become black after machining copper materials for precision parts? How to deal with it?

Since ancient times, copper has been the main raw material commonly used as industrial processed products. It has been processed into various shapes of punching products, hardware, military parts and product shells. It has a wide range of daily uses, such as drains, medals, Electrical parts, musical instruments, valves and piping accessories.

Why does the copper material of precision parts become black? Because copper is an active metal atom, chemical reactions easily occur in the presence of oxygen in the air. Most of the metals will turn black after oxidation, generating copper oxide. The chemical reaction formula is: 2cu+o2=2cuo

In many cases, the brass parts that are processed by precision parts have been oxidized and blackened before being sent to the customer, the quality is reduced, the appearance is affected, and even the rework is performed, which increases the cost.

How to deal with it?

At this time, passivation treatment should be done. The principle is to attach a layer of chemical conversion film. Because it is a chemical conversion film, it cannot be touched by hand. It does not affect conductivity, weldability, and workpiece size. The hardness will not change.

The processing process is as follows: use a stainless steel container to fill the passivation solution, put the workpiece to be processed for about 5 minutes, take out the workpiece and rinse it with water to dry it; note that before passivation, the workpiece must be pre-treated , The purpose is to prevent oil stains or oxides on the surface of the workpiece, you need to remove oil or clean oxidation first, you can use a cleaning agent or degreasing agent to remove stains, and then clean the surface to passivation protection. In order to increase the brightness of the parts, the surface can also be polished with a polishing agent before processing. The polishing process does not require any equipment throughout the process, and can be directly immersed.