Common Types of Sheet Metal Materials | Surface Treatment Methods for Steel Sheets

When it comes to sheet metal surface finishes, the following processes are commonly applied. 

1. Electrogalvanizing

Electro galvanizing is the process of forming a uniform, dense, and well-bonded metal or alloy deposition layer on the surface of a workpiece by electrolysis. Compared with other metals, zinc is a relatively cheap and easy-to-coat metal, which belongs to low-value anti-corrosion electroplating coating. It is widely used to protect steel parts, especially to prevent atmospheric corrosion, and for decoration. Plating technology includes tank plating (or hanging plating), barrel plating (suitable for small parts), automatic plating, and continuous plating (suitable for wire and strip). Electro galvanizing can generally be divided into cyanide zinc plating, zincate zinc plating, chloride zinc plating, and sulfate zinc plating. Electro galvanizing industry is a pollution industry. Although it is widely used and cheap, electro-galvanizing products do not meet ROHS standards, so electroplating products should not be used in product design.

2. Chrome plating

The process principle of chromium plating is the same as that of zinc plating. Compared with traditional galvanization, the chromium coating has extremely strong corrosion resistance, 7-10 times that of galvanization, and has a beautiful surface, but a high cost. At present, the most advanced chromium plating process is called DACROMET, which is a revolutionary high-tech metal surface treatment process with no pollution throughout the whole process.

3. Powder spraying

The powder is polarized and uniformly attached to the product surface with opposite polarity under the action of the electric field force. It belongs to physical change. The principle of the powder spraying process is mainly to polarize the coating (powder) through the electrode, and then carry the opposite charge on the object to be sprayed. Under the action of electric field force, the powder is uniformly attached to the surface of the object. Electrostatic powder spraying will not cause air pollution. The powder can be recycled to reduce the material consumption cost. The coating film has excellent acid resistance, alkali resistance, salt resistance, corrosion resistance, and adhesion.

4. Electrophoresis

Under the action of the cathode and anode, charged paint ions move to the product surface and deposit to form a coating. It belongs to the chemical change. The electrophoretic coating is applied to the cathode and anode under the action of voltage. Charged coating ions move to the cathode, and react with the alkalinity generated on the cathode surface to form insoluble substances, which are deposited on the workpiece surface. Electrophoretic paint film has the advantages of plump, uniform, flat and smooth coating, and its hardness, adhesion, corrosion resistance, impact performance, and permeability are obviously superior to other coating processes. The most common electrophoretic color is black, and other colors are also available.

5. Resin impregnation 

The product is heated in molten material, and the heated metal combines with the surrounding molten material to form a surface material with a certain thickness. Metal plastic impregnation is a new type of technical treatment method for the corrosion prevention of metal surfaces. Resin impregnation is a heating process, in which metal is preheated, dipped, and solidified. When soaking, the heated metal sticks to the surrounding materials. The hotter the metal is, the longer the soaking time is, and the thicker the material is. Dipping plastic has rich colors, good protection, excellent cold resistance, heat preservation, and acid and alkali resistance.