Tin plating and its alloy are two kinds of coating with good weldability and certain corrosion resistance. It is widely used in electronic components and printed circuit boards. In addition to physical methods such as hot dip and spraying, electroplating, dipping and electroless plating have been widely used in industry because of their simplicity.
Dip tin plating
Dipping is to immerse the workpiece into the solution containing the metal salt to be plated, and deposit the metal coating on the workpiece surface according to the principle of chemical replacement. This is different from the general principle of electroless plating because there is no reducing agent in the plating solution. It is also different from contact plating. When the workpiece is immersed in the metal salt solution to be plated, it must be closely connected with an active metal. The active metal enters the solution as an anode and releases electrons. The metal ions with high potential in the solution get electrons and deposit on the surface of the workpiece. Tin dipping is only carried out on iron, copper, aluminum and their respective alloys.
Electroless tin plating
The reducing agent used for copper or nickel autocatalytic deposition can not be used to reduce tin. The simplest explanation is that the overpotential of hydrogen evolution on the surface of tin is high, and the above reducing agents are hydrogen evolution reactions, so it is impossible to reduce tin ions to tin. To electroless tin plating, another kind of strong reducing agent without hydrogen evolution must be selected, such as Ti3 +, V2 +, CR2 +, etc. only T3 + / Ti4 + system is reported.
Advantages of acid tin plating:
1. Tin is reduced by divalent, saving power consumption;
2. The plating bath has high conductivity, low bath voltage and high current efficiency;
3. Operate the heating free equipment when the temperature is close to room temperature;
4. Gloss coating can be obtained by using appropriate additives;
5. Less damage to the substrate.
Advantages of alkaline tin plating bath:
1. Good uniformity;
2. More impurities can be tolerated;
3. Gloss can be obtained without additives;
4. Insoluble anode can be used;
5. Wide operation range;
6. Simple formula;
7. Pretreatment requirements are not high.
Tin plating is widely used in food processing equipment and containers, as well as shipping equipment, pump parts, bearings, valves, automobile pistons, tinned copper wires and CP wires, electronic components and printed circuit boards. The application of tin coating in food processing industry is due to its non-toxicity, good ductility (toughness) and corrosion resistance. The excellent ductility of the tin coating can enable the tin-plated metal plate to be processed into various shapes without damaging the tin coating. The tin coating used to protect the steel plate must be non-porous, otherwise the base steel plate will be seriously corroded in humid air.
1. Manufacturing tin cans: tin coatings are widely used in objects in contact with food and beverages due to their non-toxic nature. The biggest use is to make tin cans, such as kitchen utensils, food knives and forks, ovens, etc.;
2. Electrical and electronic industry: because tin is easy to weld and has good conductivity, it is widely used in electrical and electronic parts that need to be welded;
3. Copper wire: improve the weldability of copper wire and the barrier effect between copper wire and insulating skin;
4. Activity: because tin is soft, it can prevent scratching. It is used as a solid lubricant;
5. Prevent nitriding of steel.
Short comments: Metal products with tin-plated, in a nutshell, can protect the product itself and the application product well against corrosion. Steel drum cap seals are made of tinplate which has good quality against corrosion. Base plate only without tin-plating can also be provided if customers need.
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