Principle and requirement of substrate coating selection
Content abstract: many things in our life, such as faucets, kettles, doors and windows, even car parts, circuit boards and so on, are more or less using electroplating technology.
Many things in life, such as faucets, kettles, doors and windows, even car parts, circuit boards, etc., are more or less using electroplating technology.
In addition to increasing the beauty of the object surface, the electroplating process can also change the surface property or size of the object due to the metal coating on the surface substrate, so that it can achieve the things that its material can't do, such as giving the anti rust of the object, preventing the wear function, or improving the conductivity, lubricity, heat resistance, weather resistance and strength.
Therefore, electroplating is widely used as a surface treatment process, but not every substrate and coating can be matched with each other, and the selection of substrate and coating is also skilful. Each kind of coating has its unique properties and uses. When choosing coating, not only the application properties of coating, but also the processing technology and cost should be considered.
Requirements for coating selection:
1. Working environment and requirements of parts
The electroplating of most parts requires good protection, and environmental factors are the basic conditions for corrosion of metal materials, such as atmospheric environment (industrial atmosphere, marine atmosphere), working temperature, humidity, medium property, mechanical conditions, etc., so environmental factors are the first consideration for choosing coating. At the same time, special functions such as electrical properties and magnetic properties should also be considered.
2. Types and properties of parts
The type, physical and chemical properties of the base material have a great influence on the selection of the type and structure of the coating. For example, the protective coating of iron and steel materials in general atmosphere should adopt zinc coating, anode coating and simple structure. As copper, nickel and chromium are cathodic coatings relative to iron and steel, it is required that the coatings should have small porosity and appropriate thickness, and the corresponding pretreatment process should be selected according to the type of materials, so as to obtain a good coating combined with the collective.
3. Structure, shape and dimensional tolerance of parts
For the parts with complex structure or deep hole, the plating solution with good covering and dispersing ability shall be selected, otherwise, the coating cannot be plated on the surface of depression or deep hole, or the coating is uneven. In general, it is difficult to get a complete coating on the inner wall of the thin tubular parts, so this problem can be solved by chemical plating. For precision parts with small dimensional tolerance and strict requirements, thin layer with good performance must be used.
4. Coating properties and service life
The coating can change the surface properties of the base material and extend the service life of the parts, but it is not permanent. Especially protective coating, after a certain period of time, it still needs to be repaired or replaced. The properties and service life of the selected coating should meet the specific requirements of the parts and meet the expected purpose, so that the parts can work safely and reliably within the service life.
The properties of different coatings have both similarities and differences. Therefore, when the products are electroplated, the appropriate coating should be selected according to the different working conditions and environment, combined with the plating cost.