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Aluminum anodizing by AACOA, Inc., Niles, MI.
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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
11Aluminum Anodizing
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
12Aluminum Anodizing
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
13Aluminum Anodizing
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
14Aluminum Anodizing
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
15Aluminum Anodizing
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
16Aluminum Anodizing
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
17Aluminum Anodizing
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
18Aluminum Anodizing
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
19Aluminum Anodizing
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
20Aluminum Anodizing
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
21Aluminum Anodizing
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