Screws have to undergo surface treatment during production and processing. What is the surface treatment? Surface treatment is the process of forming a covering layer on the surface of the workpiece by a certain method. Its purpose is to endow the surface of the product with beautiful and anti-corrosion effects. The surface treatment methods are attributed to the following methods:

1. Electroplating: Immerse the electroplated part in an aqueous solution containing the deposited metal compound, and pass the current through the plating solution to precipitate and deposit the electroplated metal on the part. General electroplating includes galvanized, copper, nickel, chromium, copper-nickel alloy, etc., and sometimes blackening (blue), phosphating, etc. are also included.

2. Hot-dip galvanizing: It is done by immersing carbon steel parts in a bath of molten zinc with a temperature of about 510°C. The result is that the iron-zinc alloy on the surface of the steel gradually becomes passive zinc on the outer surface of the product. Hot dip aluminizing is a similar process.

3. Mechanical plating: impact the surface of the product through the particles of the plated metal, and cold-weld the coating to the surface of the product.
Generally, electroplating is used for screws, but hot-dip galvanizing is used for hexagonal wood screws used outdoors such as electric power and highways; the cost of electroplating is generally 0.6-0.8 yuan per kilogram, and hot-dip galvanizing is generally 1.5-2 yuan/ kg, the cost is higher.