Electrophoretic coatings use water-soluble ionic polymers as the film-forming base material. The coated workpiece can be an anode. After direct current is applied between the two poles for a period of time, a uniform and fine coating that is not dissolved by water is deposited on the surface of the coated object. A special coating method.
Under normal circumstances, the paint film is not easy to fall off. The problem of falling paint indicates that the adhesion is not good. There are many reasons for poor adhesion, such as pretreatment, coating, management, etc.
The main reason for falling paint
The pre-treatment is not clean, or the degreasing is not thorough, which makes the paint film adhesion poor.
2 electrophoretic paint
The conductivity of the bath fluid is too high, causing it to lose adhesion.
Conductivity: 550 ~ 900µS / cm (different brands, slightly different)
PH: 7.6 ~ 8.0
3 curing oven
The temperature or time is insufficient when baking, and the paint film is not completely cured.
4 profile problems
No oxide film or sealing phenomenon has occurred.
Let's analyze the specific cases in the video:
Many problems can be ruled out in the above video:
It can evenly color, which can exclude that the pre-treatment is not clean or the oil is not completely removed.
2Exclude curing temperature
Fallen paint film is cured well
3 exclude no oxide film
There are only two factors left.
1 has been sealed.
2 The conductivity of the electrophoretic paint is too high.
In its operating requirements: before electrophoresis, it must be washed with one pure water, two hot pure water, and three cold pure water, and the acid water and dirt in the surface of the profile, the inner holes and the membrane holes are fully washed. The temperature of the hot pure water tank should be controlled at 60 ~ 80 ℃ for 2-3 minutes. High temperatures lead to short times. Too long time will cause the sealing effect and reduce the profile adhesion.
The conductivity of electrophoretic paint is too high, all kinds of contamination, and the amine value will increase naturally. The bath is aged, and the paint film cannot be applied locally in severe cases. Refined in time.
In actual production, quality problems are often caused by inadequate implementation of production processes and operations. Only by continuously improving on-site management, standardizing the details of process operations, and improving the quality of personnel can we ensure the continued stability and reliability of product quality.