Generally speaking, the higher the conductivity of the electrophoretic paint bath solution, the higher the paint's swimming power. On the contrary, the electrophoretic paint manufacturer should strictly control the conductivity of the bath solution within the range specified by the process. What are the effects of electrical conductivity on electrophoretic coating? The editor introduced the factors affecting the conductivity of electrophoretic coating as follows:
1. To some extent, the conductivity can determine the amount of paint applied to the workpiece to a certain extent.
2. Low conductivity will slightly reduce the deposition of cathodic electrophoretic paint, while high conductivity will slightly increase the deposition of cathodic electrophoretic paint.
3. If the conductivity of the bath solution is too high or too low, it will also have an impact on the thickness, appearance and permeability of the electrophoretic paint film, especially with the increase of the conductivity of the bath solution, the permeability will also increase, so its film thickness will also be relatively thickened.
4. The abnormal high conductivity of the bath solution is often caused by high impurity content or low pH value, and also accompanied by abnormal changes in the film quality, such as orange peel, pinhole, or serious back-solution. It needs to be managed by ultrafiltration and anode system.
In general, the conductivity should be controlled within the range of 1200 ± 300us/cm, because the conductivity is mainly maintained by the quality assurance of deionized water before electrophoresis and the renewal of paint in the electrophoresis tank. Therefore, when the conductivity is high, it can also be adjusted by discharging ultrafiltration.
The conductivity of different kinds of cathodic electrophoretic coating bath solution also has a better control range. Based on the small change of conductivity, such as ± 100uS/cm, the film performance will not be affected, so the general control range is relatively wide, which is ± 30uS/cm. Too high or too low conductivity of the bath solution has an impact on the film thickness, appearance and permeability. With the increase of the conductivity of the bath solution, the permeability also increases, and the film thickness also increases relatively.
When the conductivity of the tank liquid exceeds the upper limit of the specified value or is on the high side, deionized water can be used to replace the ultrafiltrate to reduce the conductivity. For example, using deionized water to replace 20t ultrafiltrate for 300t tank liquid can reduce the conductivity of the tank liquid by ± 100us/cm.
