1. Metal spraying process
Process flow: pretreatment → spraying → drying.
Pretreatment is to make the coating film have strong adhesion, not easy to fall off, and long life. The surface of the parts must be pretreated before spraying. Different metal material parts pretreatment methods are not the same. Steel parts are mainly processed for degreasing, derusting, phosphating and other treatments. Commonly used water cleaning liquid decontamination and degreasing, mechanical or chemical derusting, phosphating is to immerse the parts in an acid diluent (density 1.0 ~ 1.1, pH =1～3), there will be reaction at the interface of the two. A dense phosphate film is formed on the surface of the part to improve the adhesion and rust resistance of the paint film. Aluminum and its alloy parts are mainly treated with degreasing and deoxidizing film. The degreasing method is the same as that of steel parts. The oxide film is removed by pickling, and then chemical conversion treatment is used to form a conversion film. If the surface requirements of the parts are not high, it can be omitted. Conversion processing.
The spraying process and method are also different according to the variety, performance and curing conditions of the coating. There are dozens of paints such as grease paint, natural resin, epoxy resin, phenolic resin, etc., which can be selected according to actual conditions. There are many methods for spraying, such as manual, automatic, electrostatic, electrophoresis, etc., which can be selected according to the batch size, shape and size of the parts and existing equipment.
The wear of the parts will cause the entire system to malfunction, and the spraying treatment can be used again. For example, a kinescope factory imported nearly 10,000 yuan of vibrating feeder from Japan. The disk surface is made of aluminum alloy, with a diameter of about 500-600mm. Due to long-term use, the material path is severely worn and scratches appear and cannot work normally. The problem was solved quickly and effectively after spraying with easy-curing polyamide epoxy resin.
2. The specific plan is as follows:
For pretreatment, use trichloroethane to clean the oil on the surface of the disk, and then soak in nitric acid for about 30 seconds. Just rinse it off.
Use tape to protect the surface that is not sprayed, and place the vibrating plate horizontally on the protective material (paper, cloth, etc.) to prevent paint splashing.
The ingredients are as follows: 6101 epoxy resin 1kg, 650 polyamide 0.5kg, chromium oxide 0.2kg, a small amount of talc, mix + absolute ethanol → stir evenly.
Use a manual spray gun to spray. In order to ensure the coating is even and smooth, the spray gun pressure and paint output must be adjusted. At the same time, the distance between the gun and the disk surface is kept at 300-500mm, and the spraying is carried out in three times, and the coating is as uniform as possible each time. Drying, natural drying takes about 24h; when the drying temperature is 100℃, it takes 1.5～2.0h.
The surface of the disk after spraying treatment is uniform and smooth, and the effect is good on site, and it can be used continuously for 8-12 months.
3. Conclusion
It is economical and practical to repair metal wear parts with paint, which opens up a new way for the surface treatment of metal parts.