In the control of electrophoretic coating process, oil pollution control is a very important part, if the control is not good or unreasonable choice will lead to electrophoretic paint film shrink hole, affecting the anti-corrosion performance of electrophoretic paint and the appearance effect of paint.
Electrophoresis coating in different processes will meet different sources of oil pollution, resulting in electrophoresis wet film or surface containing the corresponding oil-stained molecules, these oil-stained molecules make electrophoresis tank liquid surface or wet film surface tension changes, showing gradient changes so that the paint film in the curing level stage presents different pore-like maladie
Type of oil pollution of electrophoresis coating：
According to the source stage of oil pollution can be roughly divided into electrophoresis wet film before and after electrophoresis wet film , wherein wet film before the substrate comes with, chain pollution , electrophoresis wet film after the substrate seam folding residue , chain lubrication pollution and other oil pollution .
The substrate its own contamination
The oil pollution that comes with the substrate is mainly metal rust-proof oil in the factory and transportation process, the lalong oil in the stamping welding process, cutting oil and a small amount of metal substrate cleaning oil (e.g. heavy oil pre-wipe with gasoline).
The viscosity of this kind of oil is relatively low, most of them will usually be in the pretreatment link for degreasing water wash removal, but there are also a small number of due to the poor effect of degreasing cleaning and folding gap and internal cavity structure complex cleaning is not in place resulting in residual metal white blanks, in the workpiece into the electrophoresis tank at the same time, residual oil residue on the metal white embryo into the electrophoresis tank liquid gradually contaminated electrophoresis tank fluid, change the surface tension of the electrophoresis tank liquid. After passing through the electrophoresis tank, electrophoresis forms electrophoresis wet film, the folding gap and the residual oil in the inner cavity splash to the surface of the wet film during the process of high temperature baking, affecting the surface tension of the wet film.
Electrophoresis transport chain grease
Electrophoretic coating line transmission systems usually use chain suspension transfer, or chain skid transfer, in order to ensure its normal operation, usually need to add chain oil or grease; Chain oil and grease on the ground chain skid splash in the oven and evaporate to the surface of the paint film.
a. Compressed air oil pollution: some electrophoresis lines in the drainage process will use compressed air blowing water, some electrophoresis lines due to poor circulation effect will be in the pretreatment tank, electrophoresis tank and cleaning tank using compressed air blowing gas to increase the circulation effect, if the compressed air oil separation effect is not good lead to compressed air oil, it will lead to electrophoresis tank liquid or wet film surface oil pollution.
b. Oily ingredients in oven gas.
Electrophoresis coating oil pollution matching performance test method
Although the requirements in electrophoresis coating strict control of the above oil pollution, but there is still an inevitable risk, so in the initial oil selection and electrophoretic coating selection process need to be matched test demonstration, the selection of oil-resistant pollution performance of good electrophoretic coatings and electrophoretic coatings pollution has a small impact on the oil.
According to the type of oil pollution and pollution process, there are usually grease - electrophoretic tank liquid co-soluble test, grease - electrophoretic paint film co-baking test two test methods to evaluate the matching performance of electrophoretic coatings and oils.
Grease - electrophoresis tank liquid cosolution test
For the oils brought into the electrophoresis tank liquid: lipid oils are diluted with ether solvent 1:1, and liquid oils such as metal rust-proof oil, rolling oil for stamping welding process, cutting oil and a small amount of metal substrate cleaning oil are used Do not dilute, then follow the oil sample according to 0ppm, 20ppm, 60ppm, 80ppm, 100ppm... Such concentration to the preparation of a good electrophoresis tank liquid drip addition, after stirring 24h after the electrophoresis standard plate curing to confirm the plate shrink hole situation, until the model surface shrink hole, that is, the electrophoretic coating can tolerate the ability of the grade oil.
Grease - electrophoretic paint film co-baking test
Co-baking test for contaminated electrophoresis wet film surface oils (e.g. high temperature chain grease): 2 standard plates are washed with electrophoretic water under 20 m film thickness conditions to dry 3-5min Take 1g) drop on the aluminum surface dish, place the aluminum surface dish filled with oil sample in the center of the electrophoretic wet film model position, the electrophoresis wet film model together with the surface dish flat in the oven, according to the electrophoretic coating curing temperature after confirming the plate shrinkage situation, Recorded or rated by shrink density, e.g. 0: 0/cm2, 1:1/cm2, 2:2-3/cm2, 3: >3/cm2.