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FAQs of Galvanized Metal

Here we have summarized some frequently asked questions about galvanized metal. Please keep reading for more details!

1. What Is Galvanized Steel?

Galvanized steel is a kind of steel that is coated with a layer of zinc through the galvanizing process. According to the different galvanizing methods, it is divided into hot-dipped galvanized steel and electro-galvanized steel.

Hot dip galvanizing is a process to immerse the steel parts into the melting liquid at about 500 ℃, so that the surface of the steel parts is attached to zinc layer for the purpose of anti-corrosion.

Cold galvanizing uses electrolysis to adhere a layer of zinc to the surface of the metal. It will form a uniform and dense zinc layer that can prevent corrosion and improve aesthetics.

Hot Dipped Galvanized VS Electro-galvanized Steel

Appearance Difference

2. Is galvanized steel rust-proof?

Yes, but also no. Galvanized metal is coated with a layer of zinc, and the zinc coating is able to protect the metal from rust. It will corrode much more slowly than unpainted steel. But when the zinc coating is broken, the galvanized metal will eventually rust.

3. How long does the galvanized steel last?

The service life of galvanized steel mainly depends on the zinc coating thickness and the use environment. In normal conditions, hot-dipped galvanized steel can last more than 20 years.

4. What is galvanized steel used for?

Galvanized steel is widely used in construction, such as roofing, roof grilles, siding, wall panels, decking sheets, window frames, door panels, etc. It also can be found in home appliances, such as the bottom panels of refrigerators, shells of air conditioners, and computer parts. You can also find some galvanized steel chimneys, kitchen utensils, etc. It is also versatile in light industry, automobile, agriculture, and other industries.

Chimney Tubes

Chimney Tubes

Galvanized Buckets

Galvanized Buckets

5. About zinc layer thickness

We use the “Z+ number” to indicate the weight of the zinc layer per square meter on both sides of the galvanized sheet, for example, Z120 (Z12) means that the weight of double-sided zinc per square meter is 120 grams. Zinc coating thickness greatly affects its corrosion resistance. Generally, the thicker the zinc coating, the better the corrosion resistance. Below is a table showing the recommended zinc coating thickness for different use environments.

Use Environment Recommended Zinc layer Thickness
Indoor uses Z10 or Z12 (100 g/㎡or 120 g/㎡)
Suburban areas Z20 (200 g/㎡) and painted
Urban or industrial areas Z27 (270 g/㎡) or G90 and painted
Coastal areas Thicker than Z27 (270 g/㎡) or G90 and painted
Stamping or deep drawing applications Thinner than Z27 (270 g/㎡) or G90 to avoid coating peeling off after stamping

6. How to calculate the weight of galvanized sheet?

The density of galvanized sheet is 7.85 tons per cubic meter. The weight can be calculated according to the formula:

Weight (kg/pcs)=Thickness (mm) * Width (m) * Length (m) * 7.85

For example, if the thickness is 0.6 mm, with a width of 1.2m, and a length of 3m, the weight is about 17 kg (0.6*1.2*3*7.85).

If the coil is 5 tons, with 0.45 mm in thickness and 900mm (0.9m) in width, how long is it?

The length (m) = weight (kg) / (thickness*width*7.85) That is, the length is about 1572.7 m (5000/(0.45*0.9*7.85).

7. Is galvanized steel magnetic?

Yes, the galvanized steel is magnetic. Galvanized steel is made of iron or steel, which is coated with a layer of zinc coating. Well, iron and steel products are magnetic.

8. Can galvanized steel be welded?

Yes. But the zinc layer may cause some problems, such as welding cracks and pores, oxide slag inclusion, etc. Please choose suitable welding equipment and technology.

9. Can galvanized steel be painted?

Yes, but do not paint straight onto galvanized steel. It may stick at first, but it is easy to peel off.

10. Galvanized steel code

The common codes (Chinese standard) are DX51D+Z, DX52D+Z, DC51D+Z, DC52D+Z, S350GD+Z, and so on. Let’s take DC51D+Z for example. The first letter D means flat steel for cold forming; the second letter C means the base metal is CR steel; If the second letter is D, it means that the substrate is HR steel. The number 51-57 indicates the steel grade. The D after the number means hot dip galvanizing; Z means the zinc coating; if the letters are AZ, it means it uses galvalume coating. Here is another example, S350GD+Z. S means structural steel; 350 means the minimum yield strength is 350Mpa; G means that the characteristics of the steel are not specified; D means hot-dip galvanizing, and +Z means that the coating is zinc. Below is a table for your reference.

JIS Standard Z12 Z18 Z22 Z25 Z27 Z35 Z43 Z50 Z60
Zinc (g/m2) 120 180 220 250 270 350 430 500 600
ASTMA525 A40 A60 G60 G90 G115 G140 G165 G185 G210
Zinc (g/m2) 122 183 183 275 351 427 503 564 640

11. Tolerance Allowed

According to Chinese Standards, the allowable tolerance of width and length is 2 to 7mm;

When the width is between 600-1,200 (mm), the allowable tolerance should be within 2-5 mm;

If the width is 1,200 (excluding)-1,500 (mm), the allowable tolerance should be within 2-6 mm;

When the width is more than 1,500 mm (excluding), the deviation allowed is 3-7 mm.

If the thickness is less than 2 mm, the allowable tolerance is 0.002-0.004 mm. The thicker the galvanized steel, the greater the allowable tolerance.

When purchasing, you can inform us of your special requirements in advance.

12. What color is galvanized metal?

Hot dipped galvanized metal is silver gray, bright and shiny, with spangles (or no spangles). Its surface is rough; while electro-galvanized is smooth but dark. The appearance of galvanized steel will be different. But the galvanized steel is unqualified if it with the following defects, for example, partial without coating, blistering or serious streaks, mechanical rubbing, etc.

If you have other questions, please feel free to contact us. We will get back to you in 12 hours.

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