Analysis of the reasons for the blackening of screw fasteners

Screw blackening is a very common product surface treatment process, but it is also a very important process. Poor blackening will also lead to an increase in the defective rate of screw fasteners. In severe cases, screw fasteners may be scrapped.

Analysis of the reasons for the blackening of screw fasteners

Screw fasteners

Then why does the screw fastener appear bad when it is black?

1. The blackening surface treatment process of the screw fastener is simply to coat the screw with a layer of black film. This is related to whether the screw and the coating can be completely attached together. Stainless steel screw fasteners are prone to peeling off after being coated with black, especially after one use. The coating peeling situation will be more serious.

2. The blackening and replating of screw fasteners will cause difficulty in cleaning. After electroplating, it is easy to appear black spots on the teeth and the bottom of the teeth. If the pickling time is Long, although the appearance may be guaranteed, it is also easy to cause the screw fasteners to be more than regular. (Guide: What are the common types of fasteners?)

3. If it is a high-carbon steel material, the longer the pickling time, the greater the risk of hydrogen embrittlement of the screw fastener, and the back plating will increase the risk of hydrogen embrittlement of the high-strength screw. For high-strength electroplating products, it is best to finish electroplating at one time without rework. This requires the technical strength requirements of electroplating manufacturers to reduce the risk of hydrogen embrittlement of high-strength screws under the premise of ensuring the appearance.

Analysis of the reasons for the blackening of screw fasteners

Screw fasteners

So when we buy this kind of electroplating products, how should we avoid the defective products of this kind of screw fasteners?

1. If the product has a low tensile strength, we can specifically request the electroplating manufacturer to increase the pickling time, sacrifice the regulation, and ensure its appearance.

2. The need for product production and assembly. When purchasing screw fasteners, try to choose natural or galvanized products. These two types of electroplated products have a high safety factor.

3. If the product is indeed black screw fasteners, please check the performance of the screw, appearance, and torque of the screw when you buy it.

4. If the production requires black fasteners, then we can change the surface treatment method. In addition to black coating, we can also plate black zinc and dacromet black.

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