Galvanizing is a method of creating a zinc coating on the surface of iron and steel products to protect the product from rusting under the impact of the environment and weather over time. So what is the difference between the two popular galvanizing methods today, hot-dip galvanizing and cold galvanizing? Join us for a detailed look at the information related to these two methods and compare cold galvanizing with hot-dip galvanizing.
Humans are constantly looking for ways to improve the life of metal materials in corrosive environments. One of the most widely used techniques to protect metals (mainly steel) is galvanizing. Hot-dip galvanizing and cold galvanizing are the two most popular names on the market. To better understand the difference between the two methods when choosing, let’s explore the definition, application, and process in the content below.
Cold galvanizing is a more straightforward technique that involves painting zinc-rich paint on the material’s surface to protect it against corrosion and improve its appearance. Galvanized paint can be applied using a brush, roller, spray gun, or electroplated. Galvanized paint, unlike regular paints, has a bonding component that allows the zinc in the paint to bind with the metal mechanically. As a result, an adhesive coating with a high level of protection is created.
Like hot-dip galvanizing, cold galvanizing also offers two types of protection: passive and cathodic protection. To get the most excellent paint look, make sure the surface is clean and dry and remove any dirt or rust stains.
Cold galvanizing technology has high advantages because it can be used in many different plating fields. Currently, cold galvanizing technology is also an effective solution to replace hot galvanizing gradually. Accordingly, it is often applied to galvanize materials with complex, large, and fixed structures such as pipes, tanks, seaports, irrigation works, and bridges metal used for a long time, good corrosion resistance with time. Galvanizing paint is relatively simple to do, which is why it has become increasingly popular in plating in recent years.
Description of the cold galvanizing method: This plating technology applies a layer of liquid zinc to the metal surface. It is almost like you paint a layer of paint at an average temperature. Then, a stream of compressed air is blown into the liquid solution to form a beam of zinc particles that shoot onto the surface of the plated metal. When the air is done, the zinc coating solution and additives will stick very firmly to the metal surface, and after a few hours, they will harden and create a protective layer on the surface.
Galvanizing creates a protective layer on the metal surface from oxidation and wear, thereby helping the metal be more robust and have a longer service life. Of the three widely used galvanizing methods, hot-dip galvanizing, electrolytic galvanizing, and cold galvanizing, hot-dip galvanizing are the most common.
To galvanize metal by the hot-dip method, we dip the metal to be galvanized into a bath of molten zinc at temperatures of around 840°F (449°C). This method causes the outer layer of the metal to be melted into an alloy with zinc. This helps to coat the zinc on the metal surface evenly and makes it difficult for the zinc layer to peel off, helping to protect the substrate surface effectively.
The application areas of hot-dip galvanizing can be mentioned as chemical industry, pulp, paper, automobile manufacturing, telecommunications, lighting, and transportation…, but are not widely used in steel factories. Most of the industries that apply this method uses a large amount of iron and steel, but often rust due to oxidation under the influence of the environment. The hot-dip galvanizing technology has improved corrosion control and extended the life of items and works.
The galvanizing reaction occurs when the temperature is between 454°C & 465°C. Completely immerse the surface-prepared and dried metal in the galvanized bath. The molten zinc will wet the metal surface, and a galvanizing reaction will occur, forming zinc alloy layers. When the temperature in the galvanizing bath reaches the melting point (standard temperature is 454°C), the galvanizing reaction is complete. Carry out slag scraping on the molten surface and combine with vibration to remove excess. Then dip the product into the chromate solution to create a protective layer for the surface.
During the galvanizing process, care should be taken to completely immerse the metal in the tank for an even coating. In addition, depending on the desired thickness of the galvanized layer, it is necessary to align the corresponding dipping time. Avoid dipping for too long, causing the plating to be too thick, reducing adhesion and not aesthetically pleasing.
After studying the details of cold galvanizing and hot dipping galvanizing, we can draw some comparisons as follows:
Hot-dip galvanizing is a chemical treatment that involves electrochemical reactions. Meanwhile, cold plating is a simple physical method, just applying a layer of paint to the surface.
Both methods work to protect the inner metal layer from corrosion and rust. However, the protection of hot-dip galvanizing will be much higher than that of cold galvanizing. Because the thickness of the hot-dip galvanizing layer is more increased, it covers the entire inside as well as the outside of the material.
Although not as protective as hot-dip galvanizing, cold galvanizing has its unique benefits. This is a quick and effective method on hard-to-reach structures, fixed components. Hot dipping is also far more costly than cold plating and takes a huge number of people to complete.
As can be seen, cold galvanizing and hot dipping galvanizing have different properties and benefits. The ultimate choice of galvanizing method is finding the right balance between cost and coating performance for a given application. Besides, the choice of service to perform the construction of the material protection system is critical in deciding the structure’s ultimate efficacy.
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