Precautions for bolt blackening treatment

Precautions for bolt blackening treatment

(1) The blackened hexagonal bolts must be thoroughly degreased after blackening treatment. Because the black liquid at room temperature is acidic and has no ability to remove oil, it relies entirely on removing the oil through pre-treatment. There are many methods for removing oil, and they are chosen according to their own conditions. After degreasing, it is best to rinse and rinse. The oil stains floating on the rinsing tank must also be removed in a timely manner to prevent further contamination of the workpiece. The way to check the oil removal effect is to observe that there should be a uniform and continuous water film on the surface of the workpiece. If water droplets appear or the water film is uneven and discontinuous, it indicates that there is oil on the surface that has not been removed and should be reworked without hesitation.

(2) Carefully observe and master the growth time of the blackening film of various materials for the blackening treatment of the blackened hexagonal bolts. When a uniform gray black film is formed, the groove will be released. Stay in the air for 1-2 minutes before entering the next process. After soaking in dehydrated rust proof oil, the blackness of the film will increase and the adhesion will be better. This method helps to obtain a good covering film and the lowest cost.

(3) When the blackening process of hexagonal bolts at room temperature is completed and they remain in the air, the quality of the blackening film should be spot checked. If there are spots, exposed bottoms, or black spots on the hands, do not force yourself to enter the next process, especially the oil immersion process, and promptly check and eliminate the cause.

(4) There are generally two situations where the film layer falls black: one is poor pre-treatment, and the other is that the blackening time is too long. The method of judgment is to check whether the blackened film layer exposes the substrate. If the substrate is not exposed, it indicates that the blackening soaking time is too long. If the substrate is exposed, the pre-treatment should be carried out again.

(5) The blackening treatment of the blackened hexagonal bolt maintains the working fluid concentration of the degreaser and hydrochloric acid, especially the concentration of hydrochloric acid. It is the material basis for ensuring the quality of pre-treatment.