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Thermal diffusion galvanizing vs. hot dip galvanizing

Galvanization or galvanizing is the process of applying a protective zinc coating to metal to prevent rusting. The most common method is hot dip galvanizing, in which the parts are submerged in a bath of molten hot zinc.

Although hot dip galvanizing has been utilised to protect metal for generations, the ArmorGalv® thermal diffusion galvanizing process has emerged as a superior product thanks to new technologies and creative chemistries.

So, what are the key differences between thermal diffusion and hot dip galvanizing?

Thermal diffusion galvanizing

ArmorGalv® is a trademark name for the company’s thermal diffusion galvanizing process. The technology was borne out of the traditional sherardising process, which involves heating up metal components in a rotating drum.

The ArmorGalv® thermal diffusion galvanizing technology uses a metallurgical vapour diffusion process to apply a uniform, sacrificial, zinc-iron coating to ferrous and certain non-ferrous materials. The corrosion-resistant and abrasion-resistant coating help increase part life in harsh environments.

In contrast to other galvanizing methods, ArmorGalv® thermal diffusion galvanizing does not leave any areas of the product ungalvanized. This is because the formation of a zinc coating by means of diffusion is not hampered by the product’s geometry.

With thermal diffusion galvanizing, the diffusion time is about two hours; depth of diffusion into the substrate is 10 microns, average iron content in the coating is about 18 per cent and the average coating hardness is about 400 Vickers. ArmorGalv® consists of alloy layers only; there is no pure zinc on the surface.

Hot dip galvanizing

Hot dip galvanizing is a metal protection process that uses a molten batch of zinc to coat iron and steel with a protective layer.

The hot dipping process has been the go-to for metal corrosion protection but has several limitations. It involves many variables which can impact the appearance and characteristics of the finished product. Plus, the dipping method is unsuitable for a certain materials and complicated product shapes.

With hot dip galvanizing, the diffusion time is about two minutes; depth of diffusion into the substrate is one-micron, average iron content in the coating is about two per cent and the average coating hardness of the alloy layers is about 250 Vickers. When an item is withdrawn from a molten hot dip galvanizing bath, pure zinc solidifies on top of the alloy layers and generally makes up half the coating thickness.

Why choose ArmorGalv over hot dip galvanising?

It lasts longer

Thermal diffusion galvanizing will conservatively last two to three times longer than an equivalent coating thickness of hot dip galvanizing. This is because:

It is environmentally friendly

The thermal diffusion galvanizing process produces zero landfill material, uses limited water and is a chrome-free, non-toxic coating. Hot dipping produces toxic fumes and run-off which can pollute environments.

It offers stronger corrosion protection

The process penetrates the surface and coats the metal with the zinc-iron alloy. Hot dip galvanizing only covers the metal surface. Stronger protection can double or triple a product’s life cycle.

It can be used on ferrous and certain non-ferrous materials

ArmorGalv® has been designed to protect almost every type of metal. It can coat steel, cast iron, stainless steel, powdered metal parts and aluminium. Unlike hot dip galvanizing, ArmorGalv can be applied to springs and other specialty metals.

It will highlight imperfections

The ArmorGalv® process coats the metal with corrosion protection but will not hide any imperfections or cracks. If there are any existing cracks, they will show through the coating. This gives you peace of mind knowing ArmorGalv® will show when your products are not safe to use. Hot dipping is more likely to hide the cracks underneath the coating and can cause longer-lasting damage to your metal products.

It reduces the risk of hydrogen embrittlement

During the hot dip galvanizing process, hydrogen may be absorbed in the steel from the hydrochloric acid during the post treatment pickling process.

ArmorGalv® doesn’t pickle but blasts products during the thermal diffusion galvanizing post treatment which aids in stress relieving and reduces hydrogen embrittlement.

Recommended industry applications

  • Construction

ArmorGalv® provides a uniform, even coating on products with complicated shapes. High impact and wear resistance mean thermal diffusion galvanized products can be used for longer, despite repeated assembly and dismantling.

  • Mining

Thermal diffusion galvanized components have been used in the mining industry worldwide for decades due to the reliable and multifunctional zinc-iron alloy. ArmorGalv® is used to coat roof support rock bolts in hard rock, underground mines.

  • Rail

Pressure springs, snap fasteners and rail clips retain their properties during thermal diffusion galvanizing. They are impact and wear resistant, but still malleable enough to ensure that no cracks appear when they move to provide elasticity.

  • Transport

Suitable applications include components for spring and dampening systems, container seals and lashing eyes. Rivets are thermal diffusion galvanized because the unique properties of the zinc-iron alloy are preserved after distortion.

Get in contact with ArmorGalv Australia today to discuss how thermal diffusion galvanizing can improve the life of your products.