Aluminum Anodizing

1Aluminum Anodizing

Aluminum AnodizingAluminum Anodizingby AACOA, Inc.by AACOA, Inc.

2Aluminum Anodizing

Aluminum is “rusted”Aluminum is “rusted” artificially and uniformlyartificially and uniformly

Electricity and Chemicals requiredElectricity and Chemicals required electrical current passes through electrical current passes through

aluminum immersed in an acid aluminum immersed in an acid solutionsolution

What is Anodizing?What is Anodizing?It is an electrochemical

oxidation of the aluminum surface to produce a stable film

of aluminum oxide (Al2O3).

3Aluminum Anodizing

Abrasion ResistanceAbrasion Resistance only diamond is harderonly diamond is harder

Corrosion ResistanceCorrosion Resistance withstands salt spray and CASS testingwithstands salt spray and CASS testing

Thermal ResistanceThermal Resistance aluminum substrate will melt before the coatingaluminum substrate will melt before the coating

Electrical ResistanceElectrical Resistance 800 V required to pass a current through 1 mil 800 V required to pass a current through 1 mil

of coatingof coating PorousPorous

allows for the coloring and sealing of the allows for the coloring and sealing of the coatingcoating

Anodic Coating Anodic Coating PropertiesProperties

4Aluminum Anodizing

Common Process Common Process StepsSteps

1. Racking2. Cleaning3. Etching4.Desmutting5.Anodizing

6. Coloring7. Sealing8.Unracking9. Packing10. Lab Testing

5Aluminum Anodizing

RackingRacking

Provides a secure connection for Provides a secure connection for transportation of the parts through transportation of the parts through the various chemical solutionsthe various chemical solutions

Provides a secure connection for the Provides a secure connection for the flow of electricity through each flow of electricity through each individual partindividual part

Allows for uniformity and consistency Allows for uniformity and consistency of current flow from part to partof current flow from part to part

6Aluminum Anodizing

Clean, Etch, and Clean, Etch, and DesmutDesmut

Cleaning - heated, nonetching alkaline cleaner (10 Cleaning - heated, nonetching alkaline cleaner (10 min)min) removal of most shop residues and fabrication oilsremoval of most shop residues and fabrication oils no removal of adhesives, greases, or buffing compoundsno removal of adhesives, greases, or buffing compounds

Etching - heated sodium hydroxide (0-20 min)Etching - heated sodium hydroxide (0-20 min) roughens the surface to provide a matte finishroughens the surface to provide a matte finish limited success at obscuring scratches, die lines, and limited success at obscuring scratches, die lines, and

bearing marksbearing marks removal of aluminum 0-2.5 mil (0-65 microns) per sideremoval of aluminum 0-2.5 mil (0-65 microns) per side

Desmutting - ambient acid bath (1-5 min)Desmutting - ambient acid bath (1-5 min) removes etch smut resulting from alloying constituentsremoves etch smut resulting from alloying constituents

7Aluminum Anodizing

AnodizingAnodizing Immersion in chilled 10% (v/v) sulfuric acid bathImmersion in chilled 10% (v/v) sulfuric acid bath DC current applied at densities of 8-20 amps/ftDC current applied at densities of 8-20 amps/ft22

Time varies based on coating thickness (10-60 minutes)Time varies based on coating thickness (10-60 minutes) Barrier layer formed first to a 0.0005 mil thicknessBarrier layer formed first to a 0.0005 mil thickness Coating builds to a 1.0 mil (25.4 Coating builds to a 1.0 mil (25.4 m) max. m) max.

thicknessthickness Pores develop as the acid solution dissolves the Pores develop as the acid solution dissolves the

coatingcoating 250 - 500 billion pores per square inch250 - 500 billion pores per square inch

Part dimensions increase as the coating is 40% Part dimensions increase as the coating is 40% penetration and 60% build-up from the pre-penetration and 60% build-up from the pre-anodized surfaceanodized surface

8Aluminum Anodizing

Cross Sectional View of a Cross Sectional View of a Dyed and Sealed Anodic Dyed and Sealed Anodic

Film Film

Aluminum substrate

Non-hydrated anodic coating

Hydrated anodic coating

Ni(OH)2

precipitate,absorbed dye, &hydrated coating

9Aluminum Anodizing

ClearClear HardcoatHardcoat Absorptive dyeAbsorptive dye

Uptake of organic or inorganic Uptake of organic or inorganic moleculesmolecules

Electrolytic Two-stepElectrolytic Two-step Tin DepositionTin Deposition Cobalt DepositionCobalt Deposition

OtherOther Integral ColorIntegral Color OverdyeOverdye

Types of Anodic Types of Anodic FinishFinish

10Aluminum Anodizing

Clear Anodic FinishClear Anodic Finish Translucent film allows the aluminum

substrate surface to be visible Coating thickness varies based upon

specification

Alum. Assoc. ALCOASpecification Coating Thickness

SpecificationA21 <0.1 mil or <3 microns FlashA211 0.1 mil or 3 microns 201A212 0.2 mil or 5 microns 202A31 0.4 mil or 10 microns 204A41 0.7 mil or 18 microns 215


Hardcoat Anodic Hardcoat Anodic FinishFinish

Low temperature anodizing

Coating (aluminum oxide) density greatly increased over standard anodizing

High wear or abrasive applications

1) Aluminum substrate2) Anodic Coating


Dyed Anodic FinishDyed Anodic Finish Absorption of either

organic or inorganic molecules into the pores of the coating (2-30 min)

Limitless range of colors

Typically less fade resistance than other colored anodic finishes

1) Aluminum substrate2) Anodic Coating3) Organic/Inorganic Dyestuffs


Electrolytic (2-Electrolytic (2-Step) ColorStep) Color

Step 1: Clear Anodize

Step 2: Electrolytic Color AC plating of

metal in the base of the coating pores

Bronze colors ranging from Champagne to Black (2-25 min)

1) Aluminum substrate2) Anodic Coating3) Metal Deposit - either Tin

or Cobalt


SealingSealing Unsealed - Excellent base for paint and Unsealed - Excellent base for paint and

adhesivesadhesives Hydrothermal Seal - 200-205 F (15-60 min)Hydrothermal Seal - 200-205 F (15-60 min)

Temperature drives coating hydration causing coating Temperature drives coating hydration causing coating expansion to squeeze shut the pores at the surfaceexpansion to squeeze shut the pores at the surface

Mid-Temperature Seal with Metal Salts - 180 F Mid-Temperature Seal with Metal Salts - 180 F (15 min)(15 min) Deposition of metal salts in pores and some sealing by Deposition of metal salts in pores and some sealing by

hydrationhydration Room Temperature Seal - 90 F (15 min)Room Temperature Seal - 90 F (15 min)

Creation of a “super molecule” at the surface Creation of a “super molecule” at the surface consisting of coating, metal salts, and fluorideconsisting of coating, metal salts, and fluoride

Prone to causing green tints or a fuzzy surfaceProne to causing green tints or a fuzzy surface


Unracking and Unracking and PackingPacking

Unracking - First Inspection PointUnracking - First Inspection Point AppearanceAppearance Coating ThicknessCoating Thickness Seal QualitySeal Quality

Packing - Second Inspection Point Packing - Second Inspection Point and Packagingand Packaging TypeType SizeSize MaterialsMaterials


Laboratory TestingLaboratory Testing Coating Thickness - ASTM B244 - Eddy CurrentCoating Thickness - ASTM B244 - Eddy Current Coating Weight - ASTM B137 - Acid DissolutionCoating Weight - ASTM B137 - Acid Dissolution Seal QualitySeal Quality

ASTM B136 - Modified Dye StainASTM B136 - Modified Dye Stain ASTM B680 - Acid DissolutionASTM B680 - Acid Dissolution

Abrasion Resistance - FED-STD-141 Method Abrasion Resistance - FED-STD-141 Method 6192.16192.1

Gloss - ASTM D523Gloss - ASTM D523 Corrosion ResistanceCorrosion Resistance

ASTM B117 - Salt SprayASTM B117 - Salt Spray ASTM B368 - CASSASTM B368 - CASS


Advantages of Advantages of AnodizingAnodizing

Highly durableHighly durable Inexpensive to produce and maintainInexpensive to produce and maintain Won’t chip, flake, peel or chalkWon’t chip, flake, peel or chalk Maintains metallic appearance of Maintains metallic appearance of

aluminumaluminum Environmentally friendly Environmentally friendly

No VOC’sNo VOC’s No heavy metalsNo heavy metals Byproducts aid municipal wastewater Byproducts aid municipal wastewater

treatment facilities to separate solids and treatment facilities to separate solids and neutralize pHneutralize pH


MaintenanceMaintenanceAnodizing: The Renewable Anodizing: The Renewable

FinishFinish

Accumulated dirt and stains Accumulated dirt and stains can be removed with a mild can be removed with a mild detergent applied with an detergent applied with an abrasive cleaning techniqueabrasive cleaning technique

AAMA 609.1 Voluntary Guide AAMA 609.1 Voluntary Guide for Cleaning and Maintenance for Cleaning and Maintenance of Architectural Anodized of Architectural Anodized AluminumAluminum


Metallurgical Metallurgical FactorsFactors

Alloy and temper selectionsAlloy and temper selections Mixed alloys - various Mixed alloys - various

productsproducts Extrusion, sheet, forming, Extrusion, sheet, forming,

castingcasting Extrusion defectsExtrusion defects

Hot spots, corrosion, die lines, Hot spots, corrosion, die lines, bearing marksbearing marks


Specifying Specifying AnodizingAnodizing

Aluminum Association Designation Aluminum Association Designation System for Aluminum FinishesSystem for Aluminum Finishes Example: AAM12C22A31Example: AAM12C22A31

where AA = Aluminum Associationwhere AA = Aluminum Association

where M = Mechanical finishwhere M = Mechanical finish

where C = Chemical pretreatmentwhere C = Chemical pretreatment

where A = Anodic coating processwhere A = Anodic coating process


AACOA, Inc.AACOA, Inc.

Anodizing FacilityAnodizing Facility2551 C.R. 10 W.2551 C.R. 10 W.Elkhart, IN 46514Elkhart, IN 46514Phone:Phone:574.262.4685574.262.4685Fax:Fax: 574.262.3439574.262.3439

www.aacoa.com

Extrusion FacilityExtrusion Facility2005 Mayflower Road2005 Mayflower RoadNiles, MI 49120Niles, MI 49120Phone:Phone:269.697.6063269.697.6063Fax:Fax: 269.697.6061269.697.6061

Aluminum Anodizing

Technology

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