Hot Dipped Galvanised
Disclaimer: Please note that Graepels does not provide finishing services directly. These services are handled by third parties. The information provided here is intended as a guide to offer an overview of the available finishes and other relevant details.
Understanding Hot Dip Galvanizing
Hot Dip Galvanizing is a process that involves immersing steel or iron components into molten zinc bath at a temperature of approximately 450°C (842°F). During this immersion:
Formation of Zinc-iron Alloys: Zinc reacts with the iron in the steel to form a series of zinc-iron alloy layers. This reaction produces a strong, metallurgical bond between the zinc and the base metal.
Formation of the Zinc Coating: The outer layer is composed of pure zinc. The entire coating process ensures that the metal is covered uniformly, including internal cavities and complex shapes.
When choosing perforated metal, it’s important to understand the differences between hot-dip galvanized and pre-galvanized materials. Each has its unique benefits and applications. Pre-galvanizing involves coating the steel with zinc before it is perforated.
The choice between hot-dip galvanized and pre-galvanized perforated metal depends largely on the specific requirements of the application. Hot-dip galvanizing offers superior corrosion resistance and durability, making it ideal for demanding environments and applications. On the other hand, pre-galvanized metal provides a cost-effective and aesthetically pleasing option for less demanding conditions and decorative uses.
Process Overview
- Cleaning: Metal is cleaned of all contaminants through degreasing, pickling (acid treatment), and fluxing.
- Immersion: Clean metal is dipped into molten zinc at approximately 450°C (842°F).
- Cooling: The coated metal is cooled in air or water, solidifying the zinc coating.
Note: The galvanising process involves immersing metal sheets into molten zinc. The size of the sheets that can be processed are constrained by the dimensions of the galvanizing bath itself. Typical bath sizes rage as follows:
Length: Approximately 9 meters
Width: Approximately 3 meters
The thickness of the metal sheets that can be galvanised usually ranged up to 25mm thick though this varies widely depending on the Hot Dip Galvaniser. The maximum thickness often depends on the type of metal and the ability to handle thicker sheets. Although it’s important to consider the weight for transport, handling and installation.
Benefits of Hot Dip Galvanising
Enhanced Resistance to Corrosion: The zinc coating provides a protective barrier against moisture and oxygen thus preventing rust and corrosion
Durability: The coating is hard and durable, capable of withstanding harsh environmental conditions and physical impacts.
Uniform Coverage: The process ensures complete coverage, including complex shapes and internal cavities.
Low Maintenance: Galvanized materials require minimal maintenance compared to untreated metals.
Limitations and Considerations
Appearance: The galvanized finish may have a rough texture and a spangled pattern that some may find less aesthetically pleasing.
Handling and Installation: Proper care is needed during handling and installation to avoid damaging the coating.
Initial Cost: The upfront costs of hot dip galvanizing can be high, but the long-term benefits often outweigh the initial investment.
Issues/Limitations when Galvanising Perforated Metal
Webbing: when galvanising perforated metal, it is important to use a hole’s diameter big enough or webbing can occur. This is where zinc is trapped in the holes and drysas a film within the hole. Generally, most perforators will specify 13mm or larger to avoid this issue.
Distortion and Warping: The heat involved in galvanising process can cause distortion or warping if the perforated sheet material is too thin.
Framing: warping can also occur where heavier frames and lighter panels are welded together the hot di galvansied materials hear up and cool down at different temperatures. To avoid this, we recommend Hot Dip Galvanising parts separately and mechanically fixing them together. Or, allow for expansion between the materials.
Design Considerations
Appearance: The visual appeal of hot dip galvanised is commonly referred to as non-cosmetic. The surface finish hot dip can have a rough texture and a spangled pattern; designers should consider if this finish complements the design aesthetic.
Cost: Balance the upfront costs of hot dip galvanized perforated sheets with long-term benefits such as reduced maintenance and extended lifespan. Note that Hot Dip Galvanising is one of the most cost-effective solutions for medium to long term protection.
Longevity: Hot Dip material has a longer lifespan and needs minimal maintenance and can be re-coated over time if required. This finish is extremlly durable and resistant to corrosion thus suitable for many environmental conditions.
Applications of Galvanized Perforated Metal
Construction/Architectural: Used for facades, ceilings, cladding, and structural components, sunshades, and privacy screens.
Industrial: Ideal for filters, screens, grates, and protective barriers.
Agricultural: Used in fencing, ventilation systems, and equipment exposed to the elements.