1．Wire drawing

The so-called sheet metal drawing is to lay the material between the upper and lower rollers of the wire drawing machine, the roller is attached with sand belt, through the motor, let the sheet metal pass through the upper and lower sand belt, and pull out a trace on the surface of the material，according to the difference of abrasive belt, the thickness of the traces is different. The main function is to beautify the appearance. And the wire is also called the wiping! Materials commonly used for wire drawing: aluminum and stainless steel plates are generally considered for the surface treatment of wire drawing.

2. Sandblasting

The sand particles or steel shot are hit on the surface of the sheet metal parts by compressed air, and a layer of dense pits is formed on the surface of the workpiece. The main effect is to remove dirt and rust on the surface of the workpiece, increase the adhesion on the surface of the workpiece, and prepare for the subsequent surface treatment. The surface treatment technology commonly used materials: cold rolled plate, hot rolled plate, aluminum and so on.

3. Painting

Generally refers to the liquid spray, his process has two kinds: liquid lacquer and self - dry spray paint, self drying is to let the sheet metal parts cured at normal temperature after finishing painting, it is low cost, but the effect is not compared with the paint. The color effect by spray paint will be better; the film thickness is thinner, suitable for some precision sheet metal products, but the cost is higher. The surface treatment technology commonly used materials: cold rolled plate, hot-rolled plate and so on.

Surface treatment of sheet metal processing -- spray paint

Step one: the base of the sheet metal processing products should do derusting first, such as sandblasting, phosphating and so on.

Step 2: Epoxy zinc-rich primer for the sheet metal processing products; which is mainly used for anti-rust primer of steel structures and steel products. The coating film has good physical and chemical properties, is easy to be constructed and has good supporting performance.  The main components are epoxy resin, epoxy curing agent, zinc powder, rust preventive pigment, auxiliaries and machine solvents.

Step 3: Sheet metal processing products for epoxy cast iron intermediate paint: it is used together with epoxy zinc-rich primer for long-term anticorrosive coating transition layer. Its function is to enhance the sealing and anticorrosion of composite coating, and it can also be used as anticorrosive antirust primer. The coating is strong and tough, has good adhesion and sealing, and has good compatibility with the front and back coating. Its main ingredients are: epoxy resin and curing agent, ferric oxide and anti-rust pigment

Topcoat

Step four: Do topcoat for the sheet metal processing product. It can be used for epoxy asphalt finish, chlorinated rubber finish, acrylic and polyurethane topcoat, fluorocarbon finish, etc.

 

4. Spray (also called powder spray)

It refers to that the powder is polarized and uniformly adheres to the surface of products with opposite polarity under the action of electric field force. Spray plastic features: wear - resistant, corrosion - resistant, thick film, suitable for cabinets, equipment type of thicker products, low cost, plastic powder can also be recycled. This kind of surface treatment process commonly used materials: cold rolling plate, hot rolling plate, etc.  Powder coating is one of the most common surface treatment methods for sheet metal parts.

Surface treatment of sheet metal processing -- powder coating

Electrostatic spraying: the coating (powder) is mainly polarized by the electrode, and the object to be sprayed is charged with opposite charge. Under the action of electric field force, the powder is uniformly attached to the surface of the object.

Features of powder spraying process:     

Powder electrostatic spraying will not cause atmospheric pollution, powder can be recycled to reduce the cost of material consumption, coating performance is superior acid resistance, alkali resistance, salt corrosion resistance is better, adhesion is also high.

5. Electroplating

By chemical reaction, a layer of other metal is attached to the surface of the material, which is used to increase the corrosion resistance of metal and to achieve a certain beautifying appearance. It is a kind of common surface treatment method for sheet metal parts. Such as: galvanizing, nickel plating and so on. It is mainly plated with multicolor zinc, blue white zinc, black zinc and chromium plating. The surface treatment technology commonly used materials: cold rolled plate, hot-rolled plate and so on. Electroplating is also a common method for surface treatment of sheet metal parts.

 Surface treatment of sheet metal processing -- electroplating

Types of electroplating: 

5.1. zinc plating: A. cyanide zinc plating, B. zincate zinc plating, C. chloride zinc plating, D. sulfate zinc plating.

Galvanizing industry belongs to the pollution industry, although it is widely used and low cost, but the galvanized product does not conform to the ROHS standard, so try not to use the electroplating process in designing product.

5.2 Chromium plating：The principle of chromium plating is the same as galvanizing.    

Compared with traditional zinc plating, chromium coating has strong corrosion resistance, which is 7-10 times that of zinc plating, and the surface is beautiful, but the cost is higher. The most advanced chromium plating process at present is called DACROMET, which is called dacroa in Chinese. It is a revolutionary high technology metal surface treatment process with no pollution in the whole process.

5.3 Gold-plated

5.4 Copper plating

5.5 Nickeling

 

 

6.  Anodic oxidation

The metal surface of the sheet metal parts is oxidized to form a dense protective film on the surface of the sheet metal to increase the corrosion resistance of the products. There are two ways of chemical oxidation and anodic oxidation. It usually has primary anodizing and black anodizing. This surface treatment process is commonly used as material: aluminum. It is a commonly used surface treatment method for aluminum sheet metal parts.

7.  Screen printing

The process of marking on the surface of sheet metal parts usually includes two ways: flat screen printing and transfer printing. The main principle is the same as camera film imaging principle, which is also a process of exposure. Flat screen printing is mainly used for general surface, but if there is a deep pit, you need to use transfer printing. Usually used in trademarks, use signs, warning signs, etc.

8. Phosphating

Phosphating is a common pretreatment technology, which belongs to chemical conversion membrane treatment in principle. It is mainly applied to phosphating on the surface of steel.

The main purpose of phosphating is to protect the matrix metal from corrosion to a certain extent. Used for priming before painting to improve the adhesion and corrosion resistance of paint film layer; It can reduce friction and lubrication in cold metal processing. The common materials used in this surface treatment process are cold rolled plate and hot rolled plate.

9. Plastic dipping

The product is heated in the molten material, and the heated metal is combined with the surrounding molten material to form a certain thickness of surface material. According to the raw materials used for plastic dipping, it can be divided into liquid dipping (coating) plastic and powder dip (coating) plastic. For example, the hangers, pliers, scissors, wrenches and so on of our daily clothes. The surface treatment technology commonly used materials: cold rolled plate, hot rolled plate.

Surface treatment process of sheet metal processing -- impregnation

Metal dipping is a new technology for metal surface anticorrosion. Dipping process: heating process, metal preheating, dipping and curing. When dipping, the heated metal sticks to the surrounding materials. The hotter the metal is, the longer the time is, the thicker the material is.

The characteristics of the process of impregnation：Widely used: rich color, good protection, excellent cold resistance and heat resistance, and acid and alkali resistance.

The above stated is the most important method of surface treatment of sheet metal parts.