Surface treatment method of screw fastener

Screw fasteners are the most widely used mechanical basic parts and are in great demand.

Surface treatment is the process of forming a covering layer on the surface of the workpiece through a certain method. Its purpose is to give the product surface a beautiful and anti-corrosion effect. The surface treatment methods carried out are attributed to the following methods:

1. Types of surface treatment:

1. Electroplating:

 Immerse the electroplated parts in an aqueous solution containing the metal compound to be deposited, and pass an electric current through the plating solution to precipitate and deposit the electroplated metal on the parts. General electroplating includes galvanizing, copper, nickel, chromium, copper-nickel Alloy, etc. Sometimes boiled black (blue), phosphating, etc. are also included. Our company can now galvanize (blue-white, colorful, black) and boil black , Phosphating (gray phosphorus), nickel plating (black nickel, bronze, bronze), etc.

2. Hot-dip galvanizing: 

The carbon steel parts are immersed in a molten zinc plating tank with a temperature of about 5100C. The result is that the iron-zinc alloy on the surface of the steel gradually becomes passivated zinc on the outer surface of the product. Hot-dip Aluminum plating is a similar process.

3. Mechanical plating: 

impact the surface of the product through the particles of the coated metal, and cold weld the coating to the surface of the product.

2. Operation process:

(1) Galvanized (blue and white, colorful, black)

1. Pre-treatment: thermal degreasing tank (5 tanks)-electrolytic degreasing tank (3 tanks)-derusting tank (4 tanks);

2. Electroplating: electroplating tank (20 tanks) (ammonium chloride, zinc oxide, gloss agent, softener solution);

3. Post-processing: melting tank (1 tank)-green medicine tank (1 tank)-blue and white / colorful / black).

(2) Boiled black:

1. Pre-treatment: thermal degreasing tank (4 tanks)-rust removal tank (4 tanks);

2. Boiling black: Boiling black (5 tanks) (caustic soda, sodium nitrite solution);

3. Post-processing: anti-rust oil (1 tank).

(3) Phosphating:

1. Pre-treatment: thermal degreasing tank (1 tank)-descaling tank (1 tank)-electrolytic degreasing tank (1 tank),-surface treatment (1 tank);

2. Phosphating: Phosphating (forming a film);

3. Post-treatment: dip anti-rust oil (2 tanks).

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Link to this article：Surface treatment method of screw fastener

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