Galvanized Steel Coil

  • COSASTEEL is a China manufacturer of hot-dip galvanized steel coils. 
  • Our factory has two galvanized coil production lines with an annual output of 300,000 tons, which can meet fast delivery.
  • COSASTEEL can produce ASTM A653 DX51D galvanized steel coil suitable for cold forming.

Galvanized Steel Coil Supplier

COSASTEEL is one of the best galvanized steel coils supplier and manufacturer in China, Our galvanized steel coil production line has an annual production capacity of 300,000 tons and a manufacturing speed of 150m/min. We can manufacture and sell galvanized steel coils with a width of 800-1250mm and a coating weight of 60-300g/m3. We manufacture galvanized steel coils according to EN 10346, ASTM A653 standard. We have sufficient galvanized steel coil stock for fast delivery.

Hot Dipped Galvanized Steel Sheet in Coil (GI) is produced by passing the Full Hard sheet which has undergone the acid washing process and rolling process through the zinc pot, thereby applying zinc film to the surface. It has excellent corrosion resistance, paintability, and workability due to Zinc’s characteristics. Usually, hot-dipped galvanized steel sheet and galvanized steel coil process and specifications are basically the same.

Surface Structure

Surface StructureZero SpangleBig Spangle
Weight of zinc coatingZinc > 20g/smZinc > 30g/sm
Surface Finish

Spangled galvanized steel sheet is the spangle obtained by the condensation of the zinc coating under normal conditions after galvanizing. It is mainly used in buildings and other places where there is little direct contact with the human body.

Galvanized steel sheets without spangles are mainly produced through a special production process to control the lead in the zinc pot to a certain level, or after the strip steel is out of the galvanized pot, it undergoes special treatment to control the spangles to less than a certain level. Mainly used in home appliance housing

Hot Dipped Galvanized Steel Coils Prices

The prices of hot-dipped galvanized steel coils depend on zinc thickness, steel coil thickness, packing method. If you want to buy cheap galvanized steel coils, please choose 20 grams of zinc coating/㎡, a steel coil of 0.8mm thickness, and simple packaging. please visit galvanized steel coil price and cost.

The thickness is 0.25-0.65, the zinc coating is 30-275g,

Thickness 0.65-1.2, zinc coating 30-150g.

0.25-0.65mm*1000mm, zinc coating 30-275g, FOB Qingdao $1000-1200

0.25-0.65mm*1200mm, zinc coating 30-275g, FOB Qingdao $1010-1300

0.65-1.2mm*1000mm, zinc coating 30-150g, FOB Qingdao $950-1100

0.65-1.2mm*1200mm, zinc coating 30-150g, FOB Qingdao $970-1200

Hot Dipped Galvanized Steel Coil&Sheet Production

The manufacturing of galvanized steel coil&sheet with good weather resistance, primarily used in construction.​

Galvanized production process

Galvanized steel coils production process:

  1. Uncoiler
  2. Welder
  3. Entry Looper
  4. Pre-treatment
  5. Annealing Furnace
  6. Zinc Pot
  7. Cooling Tower
  8. Water Quench Tank
  9. Skin Pass
  10. Tension Leveler
  11. Passivation Coater
  12. Exit Looper
  13. Recoiler

 

The production and processing of galvanized steel coils can be divided into three steps: first, the entire coil is pickled to remove rust and dirt, so that the surface of the galvanized steel strip can achieve a bright and clean effect; after pickling, pass ammonium chloride or zinc chloride It is cleaned in an aqueous solution or a mixed aqueous solution of ammonium chloride and zinc chloride, and then sent to the hot-dip plating tank for the galvanizing process; after the galvanizing process is completed, it can be put into storage and packaged.

Surface treatment of galvanized steel coil

Surface treatment typeCodeFeature
Chromic acid treatmentCGood corrosion resistance, suitable for bare state
Chromic acid treatment + oilingSGood corrosion resistance
Phosphoric acid treatment (including sealing treatment)PA certain degree of corrosion resistance, good paint performance
Phosphoric acid treatment (including sealing treatment) + oilingQIt has certain corrosion resistance, good paint performance, and prevents rust during transportation and storage
Phosphoric acid treatment (excluding sealing treatment)TA certain degree of corrosion resistance, good paint performance
Phosphoric acid treatment (excluding sealing treatment) + oilingVHave certain corrosion resistance, good paint performance, and prevent rust
OiledOPrevent rust during transportation and storage
No treatmentMSuitable for immediate painting

Chromate treatment of galvanized steel coils is also called passivation treatment. Through passivation treatment, the surface structure and gloss of the galvanized layer can be improved, the corrosion resistance and service life of the galvanized layer can be improved, and the bonding force of the coating and the base metal can be improved.

The purpose of oiling galvanized steel coils is a protective layer is formed on the surface of the steel coil to prevent the surface from rusting.

Types of zinc coating of galvanized steel coil

Hot-dip galvanized coils are divided into pure zinc coating and zinc-iron alloy coating according to the coating. Their common point is that the zinc content of the zinc solution in the zinc pot is the same. The difference is that the zinc-iron alloy adds an alloying process.

pure zinc coating

In the hot-dip galvanizing production line, the pre-treated steel strip is immersed in the molten zinc bath to obtain the coating. The zinc content in the molten zinc solution should not be less than 99%.

zinc-iron alloy

A zinc-iron alloy layer is formed on the entire coating through an alloying treatment process, and the iron content in the alloy coating is usually 8-15%. During the alloying process, the galvanized steel coil is heated to 550-560°C in an alloying furnace in 5-10 seconds, so as to convert all the pure zinc layer into iron-zinc alloy. Its weldability, coating performance, heat resistance, and corrosion resistance are better than ordinary galvanized sheets.

For example:

EN 10346 DX51D+Z is pure zinc;

EN 10346 DX51D+ZF is zinc-iron alloy coating.

Galvanized Coating Layer

Galvanized-Coating-Layer
  • Anti-Finger printing ,Chromated, Oiled/ non-oiled
  • Zn Plating Layer (20-120g/sm)
  • Cold Rolled Steel Sheet

American ASTM A653 standard Galvanized Steel Sheet & Coil

  • Commercial Steel (CS Types A, B, and C)

Commercial Steel is a low-carbon cold-formed steel, such as galvanized steel roof forming

  • Forming Steel (FS Types A and B)

Requires higher drawability than Commercial Steel, such as for lamp cover forming

  • Deep Drawing Steel (DDS)
  • Extra Deep Drawing Steel (EDDS)
  • Structural Steel (SS) – (33,37,40,50,80)
  • High Strength Low Alloy Steel (HSLAS)

European EN 10346 standard galvanized steel coil

Low carbon steel for cold forming (DX51D – DX54D)

  • DX51D is equivalent to Commercial Steel, curved and profiled
  • DX52D is equivalent to Forming Steel
  • DX53D is equivalent to Deep Drawing Steel
  • DX54D is equivalent to Extra Deep Drawing Steel

Structural Steels (S220GD – S350GD)

S220GD,S250GD,S280GD,S320GD,S350GD

Use structural steel for high load-bearing capacity, with a yield strength of 220-350

Galvanized steel coil Uses

Galvanized steel coil has a wide range of applications, and its advantage is that it has a long anti-corrosion period. It is mainly used for home appliances, office panels, roof sheets, automotive panels, construction and substrate of prepainted steel coils.

Car board

The use of automotive plates must first be stamped and formed, and the steel plate is stamped into the required shape and size of the part.

Then spot welding, as an important welding method for thin plate connection, has a wide range of applications in the manufacturing industry, especially in the automotive industry.

Galvanized roof sheet

The performance requirements of galvanized roof panels mainly include the mechanical properties of the material (tensile strength, yield strength, elongation), coating performance (coating type, coating thickness and coating adhesion)

Home appliance office board

Including air conditioners, washing machines, refrigerators, photocopiers, etc., household galvanized sheets are mainly used for general forming applications and stamping.

Substrate

Another use of galvanized steel coils is to be used as the substrate of prepainted steel coils. prepainted steel coils have polyethylene coatings than galvanized coils and are more durable.

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Galvanized Steel Coil FAQ

What is Galvanized Steel Coil

Galvanized Steel Coil is used cold rolled steel coil as substrates by a continuous hot-dip process. This method tightly adheres the coating to the steel with an iron-zinc alloy bonding layer formed by a diffusion process while the heated steel strip is in contact with the molten zinc. One of the drawbacks of Galvanized is that if the Zinc coating is scratched off the steel, the Steel is left unprotected, and is subject to failure.

Type of Galvanized Spangle

Galvanized with regular spangle, zinc-coated from 30g to 275g(g90). thickness from 0.15mm to 2.0mm. Regular spangle galvanized can be used in hot and wet outdoor places. For example fence, roofing, garage door, etc.

Galvanized with zero spangles, this kind of GI with brightly surface, zinc-coated from 30g to 2755g(g90). thickness from 0.12mm to 0.25mm. It could be used outdoor also. Currently mainly exported to Southeast Asia and Africa. It is cheaper than gi with regular spangle. This product can be processed later, for example, processed into stone coated tiles.

How long the service life of regular spangles and zero spangles galvanized?

Service life depends on the Scope of application. Normally 5-10years without zinc dropping. If the incision is processed, then the useful life more than 10years.

Galvanized steel coil could be oiled?

Yes, it could be oiled. 8-20g per square meters. Oiling can prevent the oxidation of galvanized sheets in a short time.

Do you accept the test of zinc coating or not?

Yes, accept the test of zinc coating. We could send galvanized steel coil samples to the laboratory that the clients required. Or Chinese SGS.

The difference between hot-dip galvanized steel coil and electro-galvanized steel coil

A Hot-dip galvanized steel coil. The thin steel coil is immersed in the molten zinc tank, and the thin steel coil with a layer of zinc is adhered to the surface. At present, the continuous galvanizing process is mainly used for production, that is, the rolled steel sheet is continuously immersed in the molten zinc plating tank to make the galvanized steel coil.

Hot-dip galvanized sheet and electro-galvanized sheet have a big difference in the amount of galvanization. The amount of hot-dip galvanizing can not be too small, generally the minimum is 50-60g/m2 on both sides, and the maximum is 600g/m2. The galvanized layer of the electro-galvanized sheet can be very thin, the minimum is 15g/m2, but if the coating is thicker, the production line speed is very slow, which does not adapt to the technological characteristics of modern units, generally the maximum is about 100g/m2. Because of this, the production of electro-galvanized sheets is greatly restricted.

Hot-dip galvanized sheet generally has a thicker zinc layer, about 10um or more, and has strong anti-corrosion ability. So it is a commonly used galvanizing process. The electro-galvanized sheet is very thin, about 3-5um, and the hot-dip galvanized surface is rough, bright and serious. If there are spangles, the electroplating is smooth and dull (soiled).

More reference: Electro Galvanized Vs Hot Dipped Galvanized

What is a big spangle and small spangle?

Large spangles are normal spangles. Large spangles can be produced according to the normal production process. The crystal nucleus diameter is not less than 0.2mm; the crystal nucleus diameter is less than 0.2mm, which is called small spangles. This kind of spangles cannot generally be identified by the naked eye. 

What to pay attention to when purchasing galvanized steel coil

Mechanical performance 

Mechanical properties can be defined as product properties that can be confirmed through tensile tests, such as yield strength, tensile strength, elongation, n value, r value, and so on. High elongation, high r value and high n value are conducive to stamping and forming

Coating performance

The coating performance of galvanized steel coil mainly refers to the corrosion resistance of the coating and the adhesion of the coating.

Corrosion resistance includes resistance to salt spray and humidity, and coating adhesion refers to the resistance of the product to cracking, peeling, and chalking of the coating during processing.