Our common to hex bolt fastener products, such as many when purchasing the surface is bright white, it is late in the bolt surface with a layer of zinc plating or other electrical plating.

One is for the sake of aesthetics, the second is to anti-corrosion, 3 it is to match the use environment is tonal, basically all is processed according to the user’s requirements.

There are three main ways of bolt blackening process, one is called low temperature blackening.

Which is the most common way, used more in the 1980s, low temperature blackening just turns the bolt into black, its fatigue resistance is general, so now, basically also eliminated.

There is also a high temperature blackening, high temperature blackening than low temperature blackening effect is better, blackened after the bolt has good wear resistance, and the surface of the black layer has a certain anti-corrosion performance.

In the installation and use, it can also play the role of lubrication. So high temperature blackening process has been the most widely used in recent years.

The last one is chemical blackening. In terms of the process effect, chemical blackening also has a certain improvement in the performance of bolts. But now with the improvement of environmental awareness, this kind of process has a certain pollution to the environment, so it is basically not used.

For the black bolt, we not only put forward the requirements for the basic material, but also the mechanical properties of its specification.

So after the bolt blackened, but also to ensure that its mechanical properties do not have an impact, which has a certain technical requirements for the pickling process.

Although the bolt blackening is only an auxiliary process, it plays a very important role in the stability of various important parameters such as the appearance of the bolt, whether the use is smooth, the length of the anti-corrosion performance, the strength of the bolt and so on.