What is the reason for the yellowing of the coating of precision automotive stamping parts?

2021-11-30 16:14:59

The residual liquid medicine and additives in the interior of precision stamping parts spit out, and the tin layer attached to the electroplating is very easy to be corroded by these substances. Cause surface oxidation and yellow coating.

Inadequate treatment and workpiece not dried will also lead to yellowing of the coating.

Adhesion of tetravalent tin, excessive additives, zinc impurity pollution in the plating bath (less likely), insufficient plating thickness, iron impurity pollution (not easy to find in the electroplating process), storage environment. These are the reasons that will lead to the yellowing of precision metal stamping parts.

Die is an essential process equipment in stamping processing, which plays an important role in product quality, prolonging product life and production efficiency. Because the die often wears out in the production process and loses its working size, it is difficult to meet the production demand. Therefore, it is very important to improve the durability of the die.

Surface treatment of automotive stamping parts refers to the process of forming a covering layer on the surface of the workpiece by some method. The main purpose is to make the workpiece surface beautiful and anti-corrosion effect. The surface treatment methods are as follows.

Electroplating: immerse the parts to be electroplated in an aqueous solution containing the deposited metal compound, and pass the current through the plating solution to precipitate and deposit the electroplated metal on the parts. General electroplating includes zinc plating, copper, nickel, chromium, copper nickel alloy, etc.

Oxidation treatment: it can be divided into chemical oxidation and anodic oxidation.

Passivation treatment: pure iron and aluminum react in concentrated sulfuric acid or concentrated nitric acid, and the atoms on the surface react with the acid to produce a dense oxide film to prevent the continuous reaction between internal substances and concentrated acid.

Electrophoresis: coating the material surface with paint under the action of external current. It is characterized by rich color, poor adhesion and difficult to control the color.

Mechanical plating: impact the product surface through the particles of coated metal, and cold weld the coating to the surface of precision stamping parts.

The methods to improve the durability of molds are generally as follows:

Improve the design of stamping die, correctly select stamping die materials, reasonably carry out Forging and heat treatment of stamping die parts, reasonably arrange stamping die manufacturing process and ensure machining accuracy, correctly select press, reasonably use and maintain stamping die.

The above are several tips commonly used to improve the wear resistance of precision stamping dies. The improvement of wear resistance can not only prolong the service life of the die, but also reduce the production cost of the die, ensure the product quality and improve the production efficiency.