Copper and copper alloys can be dyed with a dye. BH copper and copper alloy dyes are divided into three types: A, B and C. Type A is red bronze (or brown), type B is grayish black, and type C is bronze. Suitable for dyeing copper and copper alloy products, handicrafts, daily necessities and brass-plated products. Generally, Type A and Type C dyes are suitable for dyeing brass zippers, and Type B dyes are suitable for copper and copper alloy (or copper plating) products. It is reported that the dye has the advantages of fast dyeing speed at normal temperature, long service life of the solution, low production cost, no corrosion of the dyeing liquid and no staining of the cloth.　　

(1) The amount of dye and the process conditions
BH copper and copper alloy dyes (types A, B, C)
Dosage 80～120mL/L Dyeing liquid temperature 0～30°C
Solution pH (Type A) 2~3 Immersion time l~3min
Immersion pH (B, C type) 1.5 ~ 2.0

(2) Preparation and maintenance of dyes
Put 4/5 volumes of tap water in the dyeing tank, then add the calculated dyeing dose, add water to the required volume, and mix well, then use.　　
BH staining agent will gradually decrease due to consumption during use, the concentration will gradually decrease, the pH value of the dyeing solution will increase, and the dyeing time will be prolonged. Therefore, a small amount of dyeing agent should be added frequently to adjust the pH value of the solution to the process control. The range can continue to be used. After long-term use of the dyeing solution, a small amount of black precipitate may be formed and become turbid, which also affects the effect and quality of the dyeing. The dyeing solution should be filtered, and the dyeing agent should be added to the specified pH value, and can be used continuously.　　
(3) Precautions for dyeing operation
1 When the room temperature is lower than 20 ° C, the dyeing speed is slow, and the temperature can be appropriately increased to 30 ° C to increase the speed.
2 When dyeing, it is necessary to shake the dyed parts to avoid coloring due to overlap.　
3 The dyeing time should be based on the requirements for color depth.
4 Operators should wear overalls and protective gloves.
(4) Application examples
1. The process of dyeing bronze for steel-based structural parts and zinc alloy die-casting parts is as follows: pre-treatment (refer to Chapter 2) → cyanide pre-plating copper →, recycling → cold water washing → neutralization → cold water washing → acid bright copper plating or bright nickel → Recycling → cold water washing →
3% sulfuric acid activation → cold water washing → BH dye solution dyeing → two cold water washing → hot water washing → drying → partial polishing (small parts can be rolled) → spray transparent paint → drying → finished product.
2. Brass products dyed red bronze
The process is as follows: brass parts → alkaline degreasing → two cold water washing → electric de-oiling → two cold water washing → 3% sulfuric acid activation → two cold water washing → cyanide copper plating (2min) →, recycling → cold water Washing → neutralization (3% sulfuric acid) → BH copper dyeing dyeing → two cold water washing → hot water washing (70 ~ 80 ° C) → drying → partial polishing → spray transparent paint protection → drying → finished product.
3. Non-metallic handicraft dyed bronze
Non-metal handicrafts must be brightened with copper and then dyed. The process is as follows: ceramic or FRP crafts → pre-treatment → electroless copper plating → two cold water washes → acid bright copper plating per recovery → cold water washing → activation → cold water washing → BH Copper staining dyeing→washing→drying→partial polishing→spraying transparent paint protection→drying→finished product.
4. Direct dyeing of brass products
Some brass-made everyday items, such as lamps, zippers, and fine arts and crafts, can be directly stained with BH dye, such as red bronze or green bronze, without copper plating. The process is as follows: copper parts → alkaline degreasing → water washing → 3% sulfuric acid activation → water washing → copper dyeing dyeing → cold water washing → hot water washing → drying → painting → drying → finished product → packaging.