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Electrophoresis processes Introduction
Nov 20, 2018

Normally we make zinc alloy items including awards medals,keychains,belt buckles etc. which are coated designs,one of our clients make marathon medals for the 2019 events in USA by electrophoresis process which makes the items look much more delicate while the cost is higher than coating due to the specail process,introduction of electrophoresis process below: 


Electrophoresis processes are divided into anodic electrophoresis and cathodic electrophoresis. If the paint particles are negatively charged and the workpiece is an anode, the deposition of the coating particles on the workpiece under the action of the electric field force is called anodic electrophoresis; conversely, if the paint particles are positively charged, the workpiece is the cathode, and the coating particles are deposited on the workpiece. Cathodic electrophoresis.

Characteristics

The characteristics of anodic electrophoresis are: the raw material price is cheap (generally 50% cheaper than cathodic electrophoresis); the equipment is simpler, the investment is less (usually 30% cheaper than cathodic electrophoresis); the technical requirements are lower; the corrosion resistance of the coating is worse than that of cathodic electrophoresis ( It is about 1/4 of the life of cathodic electrophoresis.

The reason why the cathodic electrophoretic coating has high corrosion resistance is that the workpiece is a cathode, the anode is not dissolved, and the surface of the workpiece and the phosphate film are not destroyed; the electrophoretic coating (generally a nitrogen-containing resin) has a protective effect on the metal, and the paint used is expensive. High quality. Process The general process of anodic electrophoresis is: pre-treatment of workpiece (de-oiling → hot water washing → descaling → cold water washing → phosphating → hot water washing → passivation) → anodic electrophoresis → post-treatment of workpiece (washing → drying).

1. Degreasing. The solution is generally a hot alkaline chemical degreasing liquid, the temperature is 60 ° C (steam heating), and the time is about 20 min.

2, hot water wash. Temperature 60 ° C (steam heating), time 2 min.

3. Derusting. Use H2SO4 or HCl, for example with hydrochloric acid to remove rust, HCl total acidity ≥ 43 points; free acidity > 41 points; add cleaning agent 1.5%; wash at room temperature for 10 ~ 20min.

4, cold water wash. Wash in cold water for 1 min.

5. Phosphating. With intermediate temperature phosphating (phosphating for 10 min at 60 ° C), the phosphating solution can be used as a commercial product.

The above steps can also be replaced by sand blasting → water washing.

6, passivation. Use a drug that is compatible with the phosphating solution (provided by the manufacturer of the phosphating solution), and it can be used for 1 to 2 minutes at room temperature.

7. Anode electrophoresis. Electrolyte composition: H08-1 black electrophoretic paint, solid content of 9% to 12%, distilled water mass fraction of 88% to 91%. Voltage: (70 ± 10) V; time: 2 ~ 2.5min; paint temperature: 15 ~ 35 ° C; paint pH: 8 ~ 8.5. Be careful to disconnect the workpiece from the slot. During the electrophoresis process, the current will gradually decrease with the thickening of the paint film.

8, wash the water. Wash in flowing cold water.


A sample made by eletrphoresis process.


anodizing electrophoresis process zinc alloy item



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