Views: 37 Author: Site Editor Publish Time: 2018-03-16 Origin: www.fuchun-casting.com
Surface treatment is a process of forming a surface layer on the surface of the matrix material, which is different from the mechanical, physical and chemical properties of the matrix.
The purpose of surface treatment is to meet the requirements of corrosion resistance, abrasion resistance, decoration or other special functions of products.
Surface protection can be divided into electroplating, coating, chemical treatment layer.Electroplating can include (galvanizing, copper, chromium, lead, silver, nickel, tin, cadmium, etc.); Coating can include (paint coating, electrostatic spray, spray technology); Chemical treatment can include (blackening treatment, phosphating treatment).
Blackening is a common method of chemical surface treatment. The principle is to produce a layer of oxide film on the surface of the metal so as to isolate the air and achieve the purpose of rust prevention. The commonly used methods of blackening treatment are two kinds of traditional alkaline heating blackening and late normal temperature blackening. However, the blackening process at room temperature is not very effective for low carbon steel.
The main components of black liquor are sodium hydroxide and sodium nitrite. When the temperature is higher, it can get a good surface at about 135-155 C, but it takes only a little bit of time.
Phosphating is a process of chemical and electrochemical reaction to form phosphate chemical conversion film. The phosphate conversion film formed is called phosphating film.
The main purpose of phosphating is to provide protection for base metal and prevent corrosion of metals to a certain extent.
It is used for priming before painting, improving adhesion and corrosion resistance of paint film layer, reducing friction and lubrication in metal cold working process.
Nickel phosphorus plating is a chemical solution, which can react with carbon steel and other components, and form a layer of nickel phosphorus coating on the surface of the steel parts, effectively separating the contact between the steel components and the corrosive medium, thus achieving the purpose of anticorrosion.Its construction is to immerse the workpiece in the plating bath slowly, because it is completely soaked, so the reaction coating is even.
Surface Blackening Treatment:
1. Blackening treatment to improve rust resistance of metal products.
2. Because blackening is not easy to cause damage to metal products because of corrosion, it prolongs the service life of metal products.
Surface Phosphating Treatment:
The advantages of phosphating are the thicker film, better corrosion resistance, heat resistance, better adhesion and hardness, faster phosphating speed.
Its disadvantages are high working temperature, high energy consumption, high evaporation of solution, rapid change in composition, and often need to be adjusted, and the crystallization is not uniform.
Surface Nickel Phosphorus Plating:
1. The coating has good compactness. All the places where the solution can permeate can be well plated.
2. The coating is very smooth, and the dirt is not easy to be deposited.
3. The properties of the coating are similar to those of the metal, which do not affect the heat transfer coefficient of the heat exchanger.
4. The corrosion resistance of Ni-P plating is very high, and the temperature resistance can reach 500 degrees centigrade.
Surface Blackening Treatment:
The principle of surface blackening is to heat the metal to a very high temperature and quickly immerse in the cold water that dissolves a special agent to form a dense layer of oxide film on the surface of the metal, which is mostly blue.
When blackening, the size and finish of the workpiece have little effect on the quality and the size and appearance quality of the product will not be changed (compared with galvanizing and spray paint), so it is often used in precision instruments, optical instruments, tools, and hardness blocks.
Surface Phosphating Treatment:
Phosphating treatment is widely used in automobile, railway, electric vehicle, bicycle manufacturing, mechanical manufacturing, steel door steel window, instrument and instrument shell, high and low voltage electrical equipment, box cabinet shell and other steel structure parts for spraying, baking paint, spray plastic, rust proof, electrophoretic dip coating and so on.
Surface Nickel Phosphorus Plating:
ENP technology can be deposited on steel, copper, aluminum and other substrates. With good technological and excellent coating properties, it is widely used in electronic and computer, aerospace, chemical and chemical industry, petroleum and natural gas, machinery, automobile and motorcycle, precision instrument, food machinery, medicine, textile, municipal road administration and other industries.
