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How does electrogalvanizing technology prevent metal corrosion

June 05,2024    268     admin

Metal corrosion has always been a common problem in metal materials. Metal recycling can reduce some of the losses caused by corrosion, but about 10% of metal materials are still scrapped every year. Corrosion can cause the invalidation of metal materials and result in significant economic losses. In 2023, the economic losses caused by metal corrosion in China reached 500 billion RMB. Worldwide, the economic losses caused by corrosion exceed imagination. The losses caused by corrosion should not be calculated solely based on the mass of metal loss, but should include the energy consumed during metal smelting and recovery. At the same time, corrosion can also cause environmental pollution, such as polluting people's land and water resources. Corrosion can also cause damage to equipment, buildings, and other facilities, ranging from economic losses to endangering personal safety. Many accidents are directly or indirectly caused by corrosion. Therefore, the research on metal corrosion prevention is of great significance.

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At present, research on metal corrosion prevention is mainly divided into two categories: metal alloying and metal surface treatment. Metal alloying is the process of melting protected metals together with special metals, and improving their corrosion resistance through passivation of special metals. There are many methods for surface treatment of metals, including electroplating, chemical plating, mechanical plating, surface coating, etc. Electroplating technology has the advantages of simple process, easy control of process parameters, and low cost, and is widely used in metal corrosion prevention.

In electroplating technology, zinc coating(galvanizing) is widely used as an anode material because the standard potential of zinc electrodes is low, which can provide good protection for cathode materials. However, untreated galvanized layers are prone to oxidation and corrosion in humid environments. Therefore, surface passivation treatment is required after electroplating to improve the corrosion resistance of the galvanized layer. Since the last century, people have conducted a lot of research on anti-corrosion technology, and the electroplating technology has developed rapidly. This article elaborates and summarizes the electroplating technology.


1.1 Chemical mechanism of electrogalvanizing technology
Electroplating is the process of using electrolysis to form a uniform, dense, and well bonded metal or alloy deposition layer on the surface of a workpiece. Compared with other metals, zinc is a relatively inexpensive and easily plated metal, belonging to the low value anti-corrosion electroplating coating. Therefore, electrogalvanizing technology is widely used to protect steel parts, especially to prevent atmospheric corrosion, and is also used for decoration. Plating techniques include tank plating (or hanging plating), roll plating (suitable for small parts), automatic plating, and continuous plating (suitable for wire and strip). The chemical reaction formula of electrogalvanizing technology is:

Zn2++2e → Zn

1.2 Process flow of electrogalvanizing
The process flow of electrogalvanizing is generally as follows:
Chemical degreasing of iron parts → Hot water washing with running water → Acid washing for rust removal once or twice with running water → Electrolytic degreasing → Hot water washing → Running water washing → 1:2 hydrochloric acid activation → Running water washing → Galvanization → Water washing → Light emission → Water washing → Passivation → Two rounds of water washing → Warm water washing → Drying → Inspection → Finished product

According to the type of plating solution, electroplating methods can be divided into four types: cyanide electroplating, zincate electroplating, chloride electroplating, and sulfate electroplating.

25μm zinc coating

1.3 Summary

Electroplating has a history of over 100 years and is the longest and most commonly used wet deposition process for metal coatings in history. Electroplating plays a very important role in the protection of metal corrosion. Due to the abundant zinc resources in our country, the price is low; In addition, the electrode potential of zinc is negative compared to iron. For the steel substrate, it is an anodic coating that can provide electrochemical protection by sacrificing zinc to protect the steel substrate. After post-treatment, the galvanized layer can not only achieve a beautiful appearance, but also greatly improve its corrosion resistance. So zinc is the most widely used metal in electroplating, and according to rough statistics, it accounts for more than 60% of the total electroplating amount, making it the largest and most widely used type of plating.

Currently, the most widely used anti-corrosion technology for steel is still galvanizing. The production of steel products using zinc based and zinc aluminum alloy coatings for surface protection has reached over 40% of the annual steel production in developed countries.

In summary, the electroplating technology has a simple process, easy parameter control, and the resulting galvanized layer is bright and flat after treatment. It is widely used in metal materials such as steel and occupies a dominant position in the electroplating market. At the same time, China has abundant zinc resources and low zinc prices, making it very suitable for the development of electroplating technology. In recent years, in consideration of environmental protection, the development of electroplating technology has also focused on high efficiency, low consumption, and low emissions. Chinese electroplating factories have generally upgraded to more environmentally friendly and efficient electroplating technology.