Galvanized Steel Classification

Galvanized steel is a composite of steel and zinc. It combines the strengths of both materials, strength and plasticity of the steel, and a corrosion-resistant coating. It is used in a wide range of industries including construction, household appliances and automobiles. This post is mainly introducing the Galvanized steel classification.

In the atmosphere, the corrosion resistance of zinc is much stronger than steel, usually under the conditions of zinc corrosion resistance is 25 times the iron and steel.

Zinc plating on the surface of the steel plate, through the physical role and electrochemical role, so that steel corrosion corrosive medium from the role.

 

Hot-dip galvanizing is the use of steel and zinc melting point difference is relatively large. We know that the melting of pure iron is 1534 ℃, the melting point of zinc is only 419 ℃, so that the treated strip can be directly immersed in molten zinc liquid zinc.

We can see this schematic diagram, this is the strip after annealing so far into the zinc pot, in the case of air, zinc plated zinc after the finished zinc strip. We can see an air knife to control the thickness of the zinc layer, and then you can see there are four small red, this is if the production of alloy products, strip to re-heating in this place, 7-15% Fe content In the coating which is alloyed products, follow-up is to be cooled.

• GI (pure zinc coating);
• GA (zinc – iron alloy coating);
• 55% Al-Zn Galvalume (aluminum-zinc coating);
• 5% Al-Zn Galfan (zinc-aluminum coating);
• Aluminum (Aluminum can be divided into two categories, one is pure aluminum plating, one is aluminum-plated silicon products);
• Zinc-aluminum-magnesium products (In recent years the new coating zinc-aluminum-magnesium products, such as Zn-5Al-3Mg. Zn-Al-Mg is a family of products that can include different Mg and Al contents);

1.Hot-dip pure zinc products (GI)

Hot-dip pure zinc products are characterized by surface appearance, good corrosion resistance, good processing.

It is divided into two kinds, one is the normal/regular spangle, the other is zero spangle. Because of zinc in the liquid lead can not be extracted very pure, the surface there are always some spangle. With the growing needs of painting requirement in the automotive industry, zinc liquid lead content reduced to dozens of ppm later. We can produce products which own zero spangle or mini spangle. For some special purposes like the construction of the above or like a large spangle, we can add zinc in the lead or antimony and other elements, access to large and beautiful zinc spangle.

2.Alloyed products (GA)

This product has the advantage of coating the surface of the paint adhesion is particularly good, after painting the corrosion resistance is also very good, while its welding is also very good.

But its surface morphology is gray which is not suitable for bare use.We are not recommended this products if it does not needed painting.because it contains 7-15% of the coating inside the iron.This part of the iron will generate a very pale light red rust. Although the corrosion resistance of red rust will not be further expanded, but the appearance is not very good.

So the main use of zinc-iron alloy or in the use of coating with the occasion, just like the automobile’s outer panel and refrigerator side panels.

3.Galvalume Products (GL)

It is characterized by corrosion resistance is particularly good.The appearance of the surface is also very beautiful. Its zinc spangle looks like pretty fish scales, which is very beautiful. Therefore, you can directly use.

It is the corrosion resistance of our ordinary hot-dip galvanized 2-6 times.Its high temperature performance is also better,which can be used in the case of 300 ℃ does not change color, short-term use, at 700 ℃ also has a good Of the color retention, and has an excellent heat reflection effect.

So this kind of product is now a large number is used in the construction of household appliances industry.

Since each coating has its own characteristics, eight properties are listed here.

1. Formability
2. Corrosion Resistance
3. Sacrificial protection
4. Corrosion Resistance (after molding)
5. Paint Adhesion
6. Corrosion Resistance (After painting)
7. Weldability
8. Heat reflectivity

For corrosion resistance, the Galvalume product is the best.

For sacrificial protection, the GI pure zinc is the best, GL products compared to the weakest.

For the corrosion resistance after molding, the three GL/GA/GI are basically the same.

The coating of the paint, GA is the best.

After painting the anti-corrosion, the GA is the best.

Weldability:GA is also the best.

Heat-reflective: GL is the best.