Copper and copper alloy castings can be used directly after machining, and in order to improve the wear resistance and corrosion resistance of the castings or to change the hue of art copper castings, surface treatment is required. The common surface treatment methods are oxidation treatment, passivation treatment and Coloring.
1. Oxidation Treatment Copper and copper alloy castings can be chemically or electrochemically oxidized after machining to produce a black or blue-black oxide film on the surface of the casting. The thickness of the film is generally 0.525m. After the casting is oxidized, it should be oiled or coated with clear paint to improve the protection of the oxide film. The composition and process conditions of chemical oxidation and electrochemical oxidation of copper and copper alloy castings are shown in Table 10-3.
And Table 10-4
2. Passivation treatment Copper and copper alloy castings can be used in better environmental conditions after machining. Acid-washing passivation treatment can be used to improve the corrosion resistance of the castings. It is characterized by simple operation and high production efficiency. ,low cost. The composition and process conditions of passivation of copper and copper alloy castings are shown in Table 10-5.
3. Coloring The coloring of copper and copper alloy castings is based on the combined action of chemicals, pigments, and artistic processing to give copper and copper alloys a bronze, decorative pattern, or other color.
The coloring treatment includes a chemical coloring treatment and a surface coating treatment. The entire process includes pretreatment, dyeing and post-treatment. The pretreatment is to polish the parts first, hot water, cold water, cyanide solution, and then rinse with cold water. The dyeing process is to immerse the pretreated product in the dyeing solution to color it. After the treatment is coloring, followed by washing with hot water, alkaline water, cold water, alcohol, and then dry with sawdust, and finally coated with transparent resin to increase the wear resistance and artistic effect.
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