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Ideal for outdoor purposes, galvanized steel is coated with zinc oxide for rust protection. Zinc-oxide provides a protective coating used to prevent rust. The zinc-oxide coating compound takes longer to corrode than non-galvanized steel. As a cost-efficient process, galvanized steel offers you a maintenance-free material option used across a wide range of industries.
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How does Galvanization Work?Typically, manufacturers will dip the steel into molten zinc, which bonds itself to the steel as any other alloy would. This makes zinc more than just a protective coating because it becomes part of the steel’s chemical composition. The interior may be steel, and the exterior may be zinc, but in between are gradient mixtures of steel and zinc that combine the properties of both metals.
- Hot-dipped galvanization is the most common form of galvanization.
- You can also spray zinc onto steel, but this method creates a weaker layer of zinc.
Galvanized Steel Product OptionsCommon galvanized steel products include galvanized steel tube and galvanized steel sheet and plate.
Galvanized Steel Tube
- Common uses for galvanized steel tube include general construction purposes, manufacturing, outdoor architectural projects, and machine parts and equipment.
- Easily fabricated and weldable, galvanized sheet and plate is often used for building panels, roofing, and lighting fixtures.
Spangle in Galvanized SteelAs an aesthetic coating, spangle in galvanized steel presents a flower-shaped or snowflake-like appearance. The crystalline appearance forms by a hot-dip galvanization process where steel sheet metal is dipped into molten zinc. The sheet metal is then cooled at levels where the liquid zinc positions itself into the spangle appearance.
- Varying alloying elements factor into the size and appearance of the spangle.
- The spangle solidification process involves individual zinc atoms solidifying to a grain, thereby forming the crystalline coating.
- Common alloying elements that produce spangle include aluminum, lead, tin, and copper.
Spangle VariationsCommon variations of galvanized spangle include:
- Spangle-Free/Zero Spangle
- Zinc-coated steel sheet where spangle is not visible to the naked eye. Also known as zinc-free plating.
- Minimized Spangle
- Spangle pattern is not eye-visible. Diameter of each spangle is less than 2mm.
- Normal/Regular Spangle
- Spangle that is visible, with diameters of at least 3mm up to 12mm.
- Large Spangle
- Spangle diameters over 15mm.
Advantages of Galvanized Steel
- Rust Resistance: Iron in steel is incredibly prone to rust, but zinc acts as a protective buffer between moisture, oxygen, and steel.
- Easy Inspection: It’s fairly simple to tell how strong a galvanized coating is, just by looking at it. Quick stress tests that can tell you how thick the zinc is.
- Sacrificial Anode: This ensures that any damaged steel is protected by the surrounding zinc coating. It doesn’t matter if the steel section is completely exposed; the zinc will still corrode first.
- Longer Life: With galvanization, a piece of industrial steel is expected to last more than 50 years in average environments and can last over 20 years with severe water exposure. No maintenance required.
Disadvantages of Galvanized Steel
- Impractical to Dip Certain Items: Some steel pieces are too tiny or too huge to be hot-dipped, and it doesn’t make sense to galvanize them using other methods.
- Zinc Can Be Temperamental: It’s important to take enough time to let galvanized steel cool down and settle in, so that the zinc doesn’t peel off. Galvanization isn’t nearly as effective if the zinc is not binding to the steel. The right coating thickness must be applied.
Does Galvanized Steel Rust?While galvanized steel provides a protective zinc-oxide barrier, eventually even galvanized steel will rust. The question remains how quickly galvanized steel will rust, with some galvanization lasting upwards of 50 years or more. Some factors that increase corrosion include:
- Outdoor environmental issues such as saltwater or humidity.
- Atmospheric considerations like natural gas or acid rain.
- Temperature fluctuations.
- Air pollution.
Learn more about corrosion-resistant metal options.