The development of galvanizing has now been a very mature process. There are many products (brighteners, positioning agents, passivating agents, etc.) that can be selected in acid galvanizing and alkaline galvanizing . The selection of process depends on the work piece to be plated.
Galvanizing process can be divided into pre-treatment, electroplating, post-processing. These three steps should be worthy of attention.
Pre-treatment is to get a clean metal surface, so that zinc can be successfully deposited on the substrate metal. On top of that, the thickness of the zinc coating is from a μ to over a dozen μ. No matter what thickness is needed, a good combination of plating and matrix metal is required. The pre-treatment is nothing more than the use of acids and bases or surfactant. Either electrolysis or ultrasonic wave, it usually takes several steps to combine to clean the surface of the work piece. The clean surface is critical for electroplating.
Electroplated nuts and screws
Electroplating process: more attention should be paid to the concentration of zinc ions. Other Concentration of auxiliary salt, current size, plating time, area ratio of cathode and anode, placement method. Heavy metal impurities. Influence of organic impurities. Balance of brightener system, etc.
Post-processing: Post-treatment of galvanizing is nothing more than Is a variety of passivation, phosphating, etc., because zinc is also very lively in the air. So it is necessary to carry out a variety of passivation treatment. Passivation is generally the use of chromium-containing passivation, of course, the environmental protection requirements have improved There are also chromium-free passivators. Overall, according to the customer's requirements - such as color appearance, salt spray time, processability or other to choose a different passivation process.
Without brighteners, what will be electroplated is a pile of spongy metal. Therefore, pay attention to choose the right brightener.
Generally speaking, electroplating is based on Faraday's law. During the electrolysis process, the amount of reduced material on the cathode is proportional to the intensity of the current passed and the time of energization. That is to say, you will open the current in a short period of time, the work piece can be coated with relatively thick zinc. However, in the high area, that is, the area with a relatively high current density tends to produce phenomena such as burnt black. In addition, due to the deposition speed, the brightness may not be so good when the current is large. If the current is small, then it is almost the opposite. This depends on the condition of the production line. The situation in each production line is different.