VALIDATED Aluminum Anodizing

The Electrolizing Corporation of Ohio provides the safest non-burning aluminum anodizing process for hard coating aluminum. Our aluminum anodizing produces superior wear and abrasion resistance, compared to conventional hardcoat, and it is available in several different colors. Unlike plating, which is 100% buildup, ECO's aluminum anodizing is 50% penetration and 50% buildup.

• MIL-A-8625 Type II & III
• ASTM B-580
• AMS 2468
• AMS 2469
• AMS 2471
• AMS 2472


Anodized Aluminum - Available in Colors

Typical applications of aluminum anodizing include:
• Surgical Cases & Trays • Surgical Instrument Handles • Dental Components • Jet engine control valves, pistons and gears • Race housings for bearings • Screw threads for hydraulic jacks • Aircraft landing gear components • Spraying systems & equipment • Marine and architectural hardware • Medical handling and processing equipment • Textile machinery • Nuclear equipment • Food processing & handling equipment

Hardness / Wearability
Our hard anodizing process is the hardest anodic coating available, with greater abrasion resistance than conventional anodizing. Thicknesses range from .0001 - .003” (.00254 - .0762 mm) on many alloys, and meet abrasion resistance requirements of MIL-A-8625F Type III.

Aluminum anodizing has excellent dielectric properties. Breakdown voltages are as high as 1500 volts at .002” (.0508 mm) thickness.

You can color-code parts to simplify assembly procedures and to reduce assembly and installation errors, or to enhance the appearance of trim and decorative hardware.
Aluminum Alloys for Anodizing
Anodizing is recommended for virtually all aluminum alloys. Difficulties can arise if an order of components is manufactured from different alloys, and this is not made known to the anodizer. Each aluminum alloy has a different rate of penetration and buildup. If different alloys are processed together, different thicknesses of oxide are formed on the different alloys. This can result in "out of tolerance" components. 

Descriptions of the most commonly used aluminum alloys follows:

1100 Series. The most commonly used are bronze-gray in color at .002” (.0508 mm). The maximum practical coating thickness is .0026 - .003” (.06604 - .0762 mm). Not especially good for machining.

2000 Series. The most commonly used are 2014, 2017 and 2024. Gray-black in color at .002” (.0508 mm) to blue-gray at .004 - .005” (.1016 - .1270 mm). The maximum practical coating is .002” (.0508 mm). Excellent machining characteristics. Avoid sharp corners in design.

3000 Series. The most commonly used is 3003, gray-black in color at .002” (.0508 mm), which is the maximum practical coating. Good for machining and recommended for colored anodizing.

4000 Series. Not commonly used.

5000 Series. The most commonly used are 5005 and 5052. Both are good for machining. 5052 has excellent dielectric properties when coated to .003” (.0762 mm), the maximum practical coating. For color anodizing, 5005 is the best choice.

6000 Series. The most commonly used are 6061 and 6063. Almost black at .002” (.0508 mm), the maximum practical coating is .0025 - .003” (.0635 - .0762 mm). 6063 is used for extrusions, 6061 forms excellent hardcoat for grinding, lapping and honing. Excellent dimensional stability, although a little “stringy” to machine.

7000 Series. The most commonly used is 7075, a high strength alloy. Blue-gray at .002” (.0508 mm), the maximum practical coating is .003” (.0762 mm). Not good for grinding and lapping.

8000 Series. Not commonly used.


Important Facts About Anodizing Aluminum

  • Hard anodizing is not plating.
  • Hard anodizing works in two ways; it penetrates the part’s surface and it builds up a layer on the part’s surface.
  • The depth of penetration and amount of buildup are approximately equal, but can vary according to the aluminum alloy. The term “thickness” includes both the amount of penetration and the amount of buildup.
  • Hard anodizing a shaft .002” (.0508 mm) thick will increase the diameter of the shaft by .002” (.0508 mm). Plating the same shaft .002” (.0508 mm) thick would increase the diameter by .004” (.1016 mm), since plating is 100% buildup.
  • Before machining components, be sure to allow for the hard anodizing buildup, not a plating buildup.When you specify hard anodizing, use the term “buildup per surface” to make clear what you are requesting.
  • Exacting dimensions can be maintained when anodizing aluminum. Standard commercial tolerance is± .0002” (.00508 mm) on a coating thickness of .002” (.0508 mm).
  • The formula for cutting a “V” thread prior to anodizing aluminum is buildup per surface multiplied by 4. This will equal the pitch diameter (PD) change. A typical example: desired PD = .4050”/.4091” (7/16 NF internal thread) and coating thickness of .0018” - .0022” (.0009” - .0011” buildup per surface). Maximum PD change will be .0011”x 4 = .0044”. Minimum PD change will be .0009” x 4 = .0036”. Therefore you should machine the pitch diameter to .4094”/.4127” to allow for the anodize buildup.

Hard Anodizing Wear Cycles

  • Allowing a tolerance on hard anodizing buildup means that that you must machine closer than blueprint dimensions. For example: if a shaft diameter is to be finished at 1.5 ± .001” (38.1 ± .0254 mm), and hard anodized .002 ± .0002” (.0508 ± .00508 mm) thick, .001 ± .0001” (.0254 ± .00254 mm) buildup per surface. Your blueprint should specify “machine to 1.498 ± .0008” (38.05 ± .02032 mm)” to achieve final finish at 1.5”(38.1 mm).

Ordering Aluminum Anodizing
Four kinds of information are crucial to processing your order accurately and quickly:
• Alloy   • Buildup per surface   • Masking requirements   • Racking instructions

Aluminum anodizing can be applied to virtually any aluminum alloy. However, each alloy is different, so it is imperative that the alloy be properly designated on the drawing or purchase order.

Buildup Per Surface
Hard anodizing can be provided from .0002 - .003”, depending upon the alloy. Like other coatings, hardcoat will change the dimensions of the basic component. Unlike other coatings, however, half of the hardcoat is buildup and half is penetration. On your blueprints and purchase orders, be sure to allow for hard anodizing buildup, not plating buildup.

It may be necessary to mask the coating from being applied to threaded or bored holes, ground points, mating surfaces and other areas. Areas to be masked must be clearly specified on the blueprint or purchase order. Because of the cost involved in this hand operation, it is usually more expensive to tap holes to a standard size and mask them rather than use oversized taps to compensate for hardcoat buildup. In most cases, it will be less expensive to coat the entire component, even if coating is required on only one area.

Proper racking is essential. Each component must be racked to maintain firm electrical and mechanical contact during the aluminum anodizing process. Since each rack contact point leaves a small void in the coating, it is important for the contact to be made in a non-critical area. Your suggestions on rack placement will facilitate processing.

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Racking - Anodizing Aluminum
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