The advanced technology Thermal Zinc Diffusion (TZD) is a uniform, sacrificial, zinc-iron coating applied to ferrous items using metallurgical vapour diffusion that creates corrosion and abrasion resistance, increasing part life even in the world’s harshest environments.

In contrast to other galvanizing methods, TZD does not leave any area of the product unprotected because the process is not hampered by the product geometry. ArmorGalv® is the first plant of its kind in Australia.

ArmorGalv® TZD is a standard option for all ferrous metal products and is perfect for threaded bar and engineered fasteners, both high tensile and commercial grade. This uniform coating is poised to revolutionise the market with 1,000+ salt spray hours of corrosion resistance. TZD is a dream come true for the fastener industry with ArmorThread®.

Traditionally, fasteners were coated for corrosion resistance and proper torque tension characteristics. Since 1971, when the Japanese court found the Mitsui Mining and Smelting Company guilty of causing a severe outbreak of cadmium poisoning, cadmium has been virtually banned worldwide.

Cadmium’s main benefit was its anti-galling properties and its ability to not ‘seize’. Galling is defined as localised surface deformation between two solid sliding surfaces under heavy friction contact.

Due to increased hardness and wear-resistant properties, ArmorGalv® provides good anti-galling properties, assisted by the absence of free zinc at the surface.

Steel with tensile strengths greater than 800MPa are at risk of hydrogen embrittlement due to the acid pickling associated with surface preparation for HDG (Industrial Galvanizers, 2006).

ArmorGalv® uses blasting for surface preparation where necessary – permitted by the greater diffusion time and increased development of the TZD gamma layer.

Using temperatures above 345°C for over 90 minutes in a completely dry environment, TZD provides no chance of inducing hydrogen embrittlement, and would even relieve any residual stresses that might already be present in the product (ASTM1059A/M).

TZD provides a uniform coating thickness that follows the contours of the component exactly with no solidifying zinc at the surface, as apparent with HDG.

The consistency of the surface is produced under the diffusion action of the zinc atoms into the base metal, assisted by slow rotation within the cylindrical kiln. It not only coats but penetrates the surface. The result is a hard (38-42Rc) super abrasion-resistant coating that cannot easily be removed by mechanical means.

Today, there is the added challenge of the process being environmentally friendly, and the coating itself being nontoxic  and chrome free. In 2006, the US EPA awarded the ArmorGalv® process its prestigious MVP2 Award as the process generates practically zero landfill material and results in a chrome free nontoxic coating.

ArmorGalv®’s surface readily provides superior adhesion of powder coat, paint, rubber, silicates, or Xylan to the surface. It also has great heat resistance, unlike any other zinc-based coating, withstanding continuous service of 650°C.

The ArmorGalv® TZD is covered by the Standards ASTM1059A/M and ISO17668 with coating classes ranging from 20 to 120 microns, defining the target coating thicknesses.

This sponsored editorial is brought to you by Armorgalv. For more information, visit www.armorgalv.com.au.

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