WHY ANODIZE?

Why anodize your aluminum?

CORROSION RESISTANCE

• Increasing aluminum’s natural corrosion resistance.
• In order to increase the natural corrosion resistance of aluminum, there are many different coatings.  Generally speaking, the following list describes least to most corrosion resistance; clear conversion coating*, gold conversion coating*, Type II anodize coating, Type III anodize coating. (*Chemical conversion is also known as Alodine, or Chem Film).

  Note: Industries involved in highly corrosive environments usually specify Clear (no dye) Class 1 Type III coatings with an ultra pure water / deionized water seal.

ELECTRICAL RESISTANCE

• Anodic coatings are natural insulators while the base aluminum is electrically conductive.
• Applied Anodize Inc. Type III anodic coating with an ultra pure deionized water seal produces a voltage breakdown of > 2300 volts.
• Precision masking.
• Precision masking is the isolation of designated areas from the anodizing process.  This provides the best of both worlds, high electrical isolation AND electrical conductivity at the same time.
• We routinely use various masking agents to isolate certain sections of a complex precision machined piece of aluminum.  This way, that section of the part will remain electrically conductive, even though most of the part is anodized and therefore not electrically conductive.

SELECTIVE ELECTRICAL CONDUCTIVITY

• The electrical conductivity is achieved in many ways but the foundation is the same for all methods.  Once a few details are known, we can suggest the best method for satisfying your needs.
• If the electrical conductivity needed is going to be static, then a clear chemical conversion film, a gold chemical conversion film, or a deposited metallic film such as gold will satisfy the demands of the application. For more detailed information please contact us, so that we can suggest the optimum combination of options.
• If the electrical conductivity needed is going to be dynamic, then a more robust system will be needed.  Typically we start with a clear chemical conversion, precision mask the necessary area and then place a metallic coating on top of the base material to protect against corrosion while at the same time be hard enough to withstand the wear associated with a dynamic connection. For more detailed information please contact us, so that we can suggest the optimum combination of options.

LOW ELEMENTAL CONTAMINANT LEVELS

• When aluminum is anodized, there are no added metallic elements.
• The anodic coating is literally grown from the base material.  As the anodic coating is formed, it penetrates and grows on the base metal by converting aluminum to aluminum oxide.
• The ratio of growth/penetration for anodic coatings is typically 50/50.
• Our experience has shown very low contaminant ranges:
• Calcium: 6,000 x 10 10 atoms / cm2.
• Nickel: 500 x 10 10 atoms / cm2.
• Potassium: 5,000 x 10 10 atoms / cm2.
• Sodium: 5,000 x 10 10 atoms / cm2.

Note: 6061 Aluminum with a Clear (no dye) Class 1 Type III  2 mil coating with a Ultra High Purity Water seal is the coating used for testing.

HIGH WEAR RESISTANCE

• The wear or abrasion resistance of aluminum anodic coatings is one of the most important characteristics of hard anodized aluminum. Anodized aluminum is used for such components as pistons, cylinders, and hydraulic gear which require a very wear resistant surface.
• Type III (also known as hard coat anodize), has earned its common name because of its hardness.  Its hardness exceeds wear characteristics of other hard coatings such as electro less nickel, hard chrome, and most ceramics.
• Our hard coat anodizing process produces superior hardness and denseness — when a part is hard coated, it increases the micro finish 2-4 times (subject to the alloy and angle of the cathode).
• Although there are other anodizing process suppliers who claim that their technologies are able to meet or exceed MIL-A-8625F specification, few of them can provide quantified Taber test results to verify their commercial statements regarding abrasion resistance.
• In the METALAST Spec, Taber indices, which are the common measure for the wear of abrasion resistance of anodic coatings on aluminum alloys, are provided for three typical aluminum alloys anodized by the MLT-III process.
• The results obtained show that the MLT-III process substantially outperforms the wear resistance specification of MIL-A-8625F.
• Aluminum alloys 2024-T3, 6061-T6 and 7075-T6 were used in this experiment. 12 coupons (4″x 4″) for each alloy were anodized to 2 mil using the METALAST Type III anodizing process.

OTHER FEATURES OF OUR ANODIC COATINGS

• Heat Dissipation.
• Anodized aluminum dissipates heat better than bare aluminum.
• Black dyed anodize dissipates heat slightly better than clear anodize.  This is why heat sinks are usually anodized and dyed black for improved heat dissipation.
• Adhesion of post anodic coatings.
• By anodizing aluminum, any subsequent coatings will have a better foundation to bind to thereby giving coatings like Teflon and Itria a foundation onto which bind.
• Surface Lubricity.
• Anodic coatings can be used as a base layer for Teflon impregnation, in doing so; the surface becomes lubricated and thus provides less resistance.