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What should be done when there is precipitation in electrophoretic paint liquid?


In general, the main factors affecting the precipitation of electrophoretic paint are:


1. Impurity ions


The entry of homogeneous or heterogeneous impurity ions is bound to react with the charged resin of the paint to form some complexes or precipitates, and the formation of these substances destroys the original electrophoretic properties and stability of the paint.

The sources of impurity ions are as follows:

(1) Impurity ions inherent in the paint itself;

(2) Impurities brought in when preparing electrophoretic paint liquid;

(3) Impurities brought in by incomplete pre-treatment water rinsing;

(4) Impurities brought in by unclean water during pretreatment water rinsing;

(5) The impurity ions generated by the dissolution of phosphate film;

(6) The impurity ions generated by the anode being dissolved.


From the above analysis, it can be seen that the quality of pretreatment of coating should be strictly controlled. This is not only necessary to improve the quality of product coating, but also extremely important to maintain the stability of electrophoretic paint solution. At the same time, from the above analysis can also be illustrated that pure water quality and phosphating solution selection (matching) is how important. 


2. Solvent

In order to make the electrophoretic coating have good dispersion and water solubility, the original paint often contains a certain proportion of organic solvents. In normal production, the consumption of organic solvents with the refilling of paint work and get a timely replenishment. But if the production is not normal or the temperature is too high, resulting in solvent consumption (volatilization) is too fast and can not be supplemented in a timely manner, so that its content is reduced to the lower limit of the following, the work of the paint will also change, which makes the film thinner, and, in serious cases, it will also make the paint in the resin cohesion or precipitation. Therefore, in the process of tank liquid management, the management personnel should pay attention to the change of solvent content in electrophoretic paint liquid at any time, and if necessary, analyze the solvent content and make up the accelerated amount of solvent in time.

3. Temperature

Various paints also have an adaptive range of temperature. Temperature increase or decrease will speed up or slow down the electrodeposition process, so that the coating film thicker or thinner. If the paint temperature is too high, the solvent volatilization is too fast, easy to cause paint cohesion and precipitation. In order to make the paint temperature is always in a relative “constant temperature state”, need to be equipped with a thermostat device.

4. Solid content

The solid content of the paint not only affects the coating quality, but also affects the stability of the paint a factor. If the solid content of the paint is too low, the viscosity is reduced, which prompts the precipitation of the paint. Of course, too high solids are not desirable, because too high, the paint piece after swimming entrainment increases, the loss of increase, reduce the utilization rate of paint, so that the cost increases.

5. Circulation stirring

In the production process, the management personnel must always pay attention to whether the circulation of electrophoretic paint stirring is good or not, and whether the pressure of some instruments (such as filters, ultrafilters) is normal or not. Ensure that the paint circulates 4-6 times per hour, and the flow rate of the paint at the bottom is about 2 times of the flow rate of the paint at the surface, and don't make the electrophoresis tank form a dead corner of stirring. Do not stop stirring unless under special circumstances.