Materials like Amumetal and Amunickel require a special heat-treatment called Hydrogen Annealing to provide optimum shielding characteristics. Shielding materials reach their optimum permeabilities when they undergo this heat treating process. The annealing procedure should always take place once all fabrication has been completed, as any shock or vibration to the shield after annealing will degrade the material's performance. Strict adherence to the specified annealing cycle insures optimum magnetic shielding characteristics, boosting by increasing the material's permeability on average by 40 times.

Amuneal's standard annealing cycle consists of a dry hydrogen atmosphere with a dew point below -60°F, heated to 2150°F±50°F (1177°C) for four hours and then cooled to room temperature at a rate of 6°-9°F per minute. Our four in-house annealing furnaces are computer controlled and are monitored daily to maintain consistent performance. As the only shielding manufacturer in the industry with our own Hydrogen Annealing facility, we are able to maintain exacting performance from our materials.

With Amumetal and Amunickel, this special process removes the carbon and other trace elements from the material and relieves the mechanical stresses due to processing and fabrication. This allows the grain boundaries of nickel's crystalline structure to expand. This newly formed nickel structure creates a low reluctance path for magnetic fields to follow, thus increasing the material's permeability.

After the annealing cycle it is critical to avoid any rough handling of the material as it is extremely sensitive to shock and vibration. The newly formed crystalline grain structure of nickel is relatively fragile and any disturbance will begin to destroy the material's effective permeability.

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