Keywords: blacken, blackening, blackening film, room temperature blackening, blackening furnace, turn blue, alkaline blackening, heat treatment, pickling,

How to make the blackening film stronger?

　　When the room temperature blackening liquid was just introduced, the blackening film is not firm is the common problem of such products. This process is also the most difficult to solve the key problem of the product. Workpiece blackening after the surface of the black film adhesion is poor, serious friction with a hand that appears to fall off the phenomenon. It appears for the following reasons:  

　　1. The blackened film can be rubbed off, rubbing the color of the workpiece is significantly lighter. This phenomenon is due to the workpiece degreasing cleaning is not complete, or the existence of secondary pollution. Machined workpieces must be cleaned (because the machine tool lubricant that contains grease). Sandpaper polishing can not replace the pickling rust.  

　　2. The blackened film can be rubbed off, and the color of the workpiece is still black after rubbing. It is because the blackening treatment time is too long, resulting in the blackening layer on the surface of the workpiece is too thick. Form a blackened floating layer, so the adhesion is poor. 

　　The solution is: in the workpiece to meet the requirements of the black timely removal of the workpiece, the workpiece will continue to react to the workpiece surface after a period of time out of the liquid to further blackening. This not only saves time but also increases the service life of the liquid.

Blackening film

　　3. The workpiece is not thoroughly washed after pickling, the residual acid will be brought to the blackening solution, resulting in too fast reaction. Seriously affect the use of liquid.

　　The solution is: the workpiece should be rinsed with water after pickling. Then blackening treatment. Degreasing after washing, pickling after washing, blackening after washing do not use the same pool, and try to use live water rinse.  

　　4. floating rust on the surface of the blackening workpiece is also one of the reasons for the blackening film is not firm, the workpiece should be blackened immediately after pickling and washing.

　　5. Room temperature blackening solution and the traditional alkaline blackening is different, after blackening the workpiece in 24 hours is still in the late reaction. Therefore, check the adhesion of the blackened film should be carried out after 24 hours, with the extension of the post-effect time the adhesion of the film layer will be better and better.

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