The phenomenon of wet flake falling off occurs frequently in some units during the drying process, especially the thicker the coating is, the easier it is to fall off in wet state, the first layer is often rare, and the second or third layer is more common. Obviously, when the gravity of the coating exceeds the adhesion of the coating to the surface of the white mold, the coating flakes off, and it is completely certain that the white mold falls off from the part with the plane downward, and it is impossible to fall off the coating on the upper surface.
In this case, the following operations should be corrected:
① After the coating is dried and thickened, do not immerse the pattern in the slurry tank for too long when it is dipped again to avoid the first layer that has been dried infiltrating into “slurry”. The first layer should be fully wetted, fully rubbed, long immersion is better than fast immersion, while the second and third layers are not. If the slurry can be evenly immersed and hung, the slurry tank should be raised as soon as possible.
② After the second and third layer dip coating, as long as there is no dripping, they should be dried in the drying room as soon as possible. If they are not dried for a long time, the water in the outer layer will quickly infiltrate into the inner layer, weakening the adhesion between the inner layer and the white mold.
③ After the thick layer is dipped, the pattern shall not be placed in the same way with one side facing the sky and the other side facing the ground. For the parts easy to be infiltrated and fallen off, try not to face the ground as much as possible. Oblique, vertical or reverse placement can avoid gravity falling off.
④ Properly increase the drying temperature within the allowable range of the process, reduce the humidity of the drying room, increase the heat flow in the room, so as to accelerate the drying speed.
⑤ Increase the use of binder and improve the adhesion of coating
⑥ Try not to use or use less aggregate with large water absorption, high density or too coarse.