The answer is yes, we need to close off holes.
The detailed introduction is as follows:
Before powder coating metal parts, their surface structure is loose and there are pores on the surface. During oil removal, acid washing, activation, and electroplating processes, the solution is easy to penetrate, but it cannot be cleaned thoroughly. These residual liquids will slowly leak out during storage and use after plating, causing quality problems. In severe cases, local plating problems may occur during electroplating, and the plating solution may also be contaminated. So there is the operation of close off holes. Before performing metal surface treatment, sheet metal manufacturers will default to close off holes, so there is no need to worry about this.
Of course, the method of close off holes in powder coated parts is something many people want to know. When some precision parts are processed by powder coating, a small amount of gas residue will be generated, which can cause many small gaps and cracks in the parts. Therefore, timely treatment will be carried out to seal the gaps and improve the performance of the parts. This requires powder coating sealing technology. Taking the powder coating sealing method commonly used by Mulan Group as an example, the following is:
1. Mechanical sealing method:
The parts have a large margin for finishing, and the surface pores are closed by finishing. Other mechanical methods such as sandblasting, grinding, and polishing can also be used to deform the surface and seal the pores.
2. Steam treatment method:
Steam treatment can form a layer of Fe3O4 oxide film on the surface of parts, which can block surface pores. Fe3O4 is a dense semiconductor that does not hinder electroplating. Parts treated with steam do not require any further cleaning before electroplating.
3. Organic silicide sealing method:
Immerse the parts in a carbon tetrachloride solution containing 4% organic silicides. Preheat the parts to 200 ℃ first, and then suddenly immerse them in the above solution. After immersion, dry at 200 ℃. This can form a layer of organic silicide film on the surface of the part, which can prevent the invasion of plating solution. This method has satisfactory results for nickel plating and cadmium plating.
4. Passivation liquid filling method:
Soak the parts in a solution of 2g/L potassium dichromate, 2g/L baking soda, and the remaining water to fill the pores with passivation solution. The temperature of the passivation solution is 70-80 ℃. After electroplating, the parts are heated at 100-110 ℃, and the passivation solution is discharged from the pores through the evaporation of water in the pores. This method is suitable for galvanizing.
5. Fixed substance blockage method:
Immerse the parts in molten zinc stearate at 200 ℃ to allow it to penetrate into the pores for sealing. After immersion, excess zinc stearate on the surface should be removed before electroplating. Vacuum impregnation of resin and high soft spot paraffin is also a feasible and simple method.
Through the above introduction, we can clearly see that there are five commonly used sealing methods by powder coating manufacturers, including mechanical sealing, steam treatment, and organic silicide sealing.
The method of close off holes in powder coated parts has been explained to everyone. Friends who need to understand powder coating can seek help from Mulan Group. We have professional personnel to answer your questions, and we have served numerous sheet metal processing customers all over the world. We promise to provide you with satisfactory sheet metal customization services.
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