Hard Anodising Technical Information


The hard anodising process

Just like standard anodising, hard anodising is an electrolytic surface treatment process involving bathing aluminium components in an acid solution. This converts the base metal to form a protective oxide coating. While standard anodising is generally limited to a maximum of 30 microns, hard anodising can achieve thicknesses of up to 100 micronsby lowering the acid bath to near freezing point and increasing the voltage of the electric charge running through it.

  • First, the part is chemically cleaned with an alkaline mixture to remove surface contamination
  • The part is racked on specially coated aluminium or titanium racks designed to conduct an electric current
  • The part is bathed in an acid solution with an electric current running through it (of a higher voltage than the current applied during the standard anodising process). The temperature of the acid solution is lowered to near freezing.
  • The part serves as an anode (a positive charge).
  • The current releases hydrogen at the source of the negative charge and oxygen at the anode, creating a buildup of aluminium oxide on the surface of the part
  • The thicker oxide coating grows out of, and into, the product, and converts the surface of the material itself into a thick, protective coating
  • The hard anodised part is treated in chemical baths to seal the microscopic pores created during the hard anodising process

Components to be anodised must be free from any inserts, screws, bolts or any other items. If these aren’t made from aluminium, they will be attacked by the acids used during the process and may be damaged.

Although we use standard titanium and aluminium racks for most products, we may be required to construct special racks for some jobs, which can incur additional fees.

MIL SPEC Hard Anodising

DECO standard and hard coat anodising have been tested to meet quality standard MIL-A-8625F, type 2 (sulfuric acid anodising) and type 3 (hard coat anodising). DECO hard anodised aluminium has passed the spot dye and corrosion resistance tests, and its coating weight, thickness and abrasion resistance are all tested to MIL SPEC standards.

Quality Testing, Standards and Compliance

All of our hard anodising products are tested in our Quality Testing lab onsite, to make sure they meet the relevant Australian Standards.

DECO Industrial complies with:

AS/NZS ISO 9001:2015

DECO Industrial complies with AS/NZS ISO 9001:20015 for provision of metal finishing services including hard anodising. This means our hard anodising products meet customer needs as well as Australian government regulations.

ISO 14001 Environmental Management System Certification

We are currently in the process of attaining ISO 14001 Environmental Management System Certification, which will certify DECO Australia as being an environmentally friendly business. ISO 14001 certifies that we minimise the negative impact on the environment from our products and processes, and that we comply fully with Australian environmental laws.

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