Post on 11-Jan-2017
ALUMECO 19-5-2015
Esben ØsterB.Sc.Chem. Eng.
Working whit surface treatment since 1999 at HAI Horsens, Denmark.
10 Years as Quality Manager.
5 Years as Technology Manager.
------------------------------------------------------------------------------A/S HAI Horsens 102 år Surface treatment of
aluminium Anodizing.
AGENDA
Why surface treatment ?Anodizing mechanism. Pre-treatment.After-treatment.How to specify. Alloy.Case study.
MOST COMMON USED ALLOY
Cobbercontainingalloy.Typical 4,0-4,58 % cobber.
20072011201420172024
High strength.Good for cutting.Bad corrosion .Difficult for welding.
BoltsMachinepartsHydrauliccomponents
Magnesium containingalloy.
50055754
5005-best anodizingquality.
Facade.Otherconstruction
Magnesiumand silicon.
60606012606362626082
High strength.Good for welding.Good for decorativeanodizing.
ConstructionWindows Door
Zinkcontainingalloy
7075 Very high stength. CarAeroplaneSpace
A
Rating for different anodizing proces:
WHY SURFACE TREATMENT?
TextureGlossStructureMatt surfaceColor
Visuel properties
PittingGenerel corrosionFiliform corrosionOthers
Corrosionprotection Hardness
Electrical insulationRoughnessAbrasion resistance
Mechanicalproperties
OVERVIEW
Pretreatment
Cleaning and activate surface. Etching, blasting, Polishing. Chemical and Mechanical methods. Gloss, structure, rougness, smootness
Anodizing
Std. anodizing, hardanodizing, chromic acidanodizing, phosphos acid anodizing. Hardness, insulation, corrosion resistens, abrasionresistance, adhedsions properties.
Aftertreatment
Coloring, screen printing, sealing, organic coating.Color, increase corrosions resistance, chemicalresistance.
Pre-treatment
Mechanialmethods
Chemical methods
EFFECT OF PRE-TREATMENT
VIBRATION TECHNIQUE
Roughness.Gloss.Remove sharp edges
GRINDING
Grinding Brushing Polishing
Band Pads
BLASTING
Uniform surface.
Remove scratches.
Decorative surface.
Roughness.
MethodsGlass
Aluminium oxid
steel
Sand
Plastic
CHEMICAL PRE-TREATMENT
Alkaline etch E6Acid etchChemical brightningElektrolytic brightning
Dip or spray
EFFECT OF ETCHING
Treating time ?
ACID ETCH DEOXIDING OR E0 ETCH
Minimum attach - 0,1 micron.Keep tolerances.
No visuel effekt.
Example: diameter - 6 mm H7 +0,015 mm Alkaline etch 6 minutes. 6*3 micron =18 micron
Alternativ: Masking of hole.
CHEMICAL BRIGHTNING SEMI GLOSSDip proces.Good for complex shape.Whitout current.
Gloss up to ca. 100
Good in combination whit blastion and grinding.
Cheapest brightingmethod.
CHEMICAL BRIGTNING HIGH GLOSSDip proces.Good for complex shape.Whitout current.
Gloss up to ca. 400.
Good in combination whit blasting and grinding.
Containing HNO3.Produce hazard gassesduring brightning.
ELECTROPOLISHING
Whit current, 5 amp/dm2
Gloss up to ca. 400-500
Good in combination whit blasting and grinding.
Difficult to control.
Old proces.
Deburring effect.
ISO 7599 PRE-TREATMENT
ANODIZING
AlukseringRafbrynjunAnodiseringAnodizingElokseringAnodisierenAnodischen oxidation
Hård alukseringHörd RafbrynjunHard AnodizingHard coatTeknisk Eloksering
A lot of names
THE PROCESS
Dissoziation: 3 H2SO4 = 3 SO42- + 6 H+
Anodic reaction: 3 SO42- - 6 e = 3/2 O2 + 3 SO3
3 Al + 3/2 O2 = Al2O3
Acid formation: 3 SO3+3 H2O = 3 H2SO4
Kathodic reaction: 6 H++6 e = 3 H2
Total reaction: 3 Al +3 H2O = 3 H2 + Al2O3
Sulfuric acid
IN PRACTICE
Water
10 % sulfuric acid
ANODIC LAYER
LAYER GROWTH
Type II ca. 1/3Type III ca. ½
Vary from alloy test.
THE ANODIC LAYER
Layer thicknessDensity coating veightElements
HARDANODIZINGLower temerature.Change electrolyte.Maybe additive to electrolyte.Longer treating time.Higher current density.Better agitation.
PROPERTIES - HARDANODIZING
Hårdhed Abrasion resistanceCorrosion resistanceElektrical insolationLayer thichnessNatural colorAddition colorHeat resistance
Application for hardanodizing.Offshore, machine parts, moving parts, etc.
Bigger than 350 HV. Taber test. Maks 35 mg.Saltspray test 1000 h.Break down ca. 1500-2000 volt.30-150 micron.Brown / grey.Black, normal black.Short up to 2000 degree.
CROMIC ACID ANODIZING CAA
1-5 micron layer thichness, maximum.Natural color: grey. Different methods.
Adhesion properties, painting and bonding.Good corrosion properties.Smooth surface.
Aeroplane.Old process.
Containing Cr6+
Not RoHS.
PHOSPHORIC ACID ANODIZING, PAA
Thin layer thichness.Natural color: grey.
Adhesion properties, painting and bonding.
Aircraft and aerospace alloy sheets.
According to RoHS.
POROSITY
Number of porer, and size of the porer, gives the porosity.
WHY CORROSION RESISTANCE?
Compact surface.Electrical insulation.No bad intermediate layer.
Aluminium Aluminium
Anodic layer Paint
AFTER-TREATMENTCOLORING
Electrolytic color.UV resistance.Few color.
Organic colorNot UV resistance.Indoor application.Many color.
In generelNeed normally 15 micron.
Best whit surfuric acid method, anodizing, pore size.
Spray or dip process.
AFTERTREATMENT
In OrganicUV stabileOutdoor useLess numbers of color
Organic pigmentnot UV stabile.Indoor Many color
anodic producedoxide layer
anodic producedoxide layer
anodic producedoxide layer
Integral Colouring:
Adsorptive Colouring:
Electrolytic Colouring:
oxide layer withinherent colour
barrier layeraluminium
barrier layeraluminium
barrier layeraluminium
adsorbed dye
electroplatedmetal
THE DIFFERENT COLOURING METHODS
MANY COLOR
Dip proces
Alloy
Jigging
SEALING CORROSION RESISTANCE
Dicromatsealing, not RoHS.Hot water sealing, Bøhmit.Cold sealing, Nickel and Cobalt.
Reduce hardness and abrasion resistance, approx. 20 %.Dicromate gives gren color.Others are invisible.
RESISTANCE - CHEMICAL
Corrosion resistance.Neutral pH (6-9).
Organic coating can improve properties.pH resistens.
Painting and unsealed pre-anodic layer.
5-8 micron + topcoat big amount of color, including white.
PTFE ON ANODIC LAYER
Extra corrosion resistance.Non stick.FDA approvel.Chemical resistanceHigh temeratur.Low friction. Many color.
Need baking.
Many different methods.
Also multi layer systemNavn Kemisk navn Kemisk struktur Temp.
max. Cc Smeltepunkt
C PTFE Polytetra-
fluorothylenF F
-C-C-F F
260 18 327
PVDF Polyvinyliden-fluoride
F H -C-C-F H
140 25 170
E-CTFE Ethylen chloro-trifluorethylene
H H F F-C-C-C- C-H H CL F
150 31 245
FEP Fluorinated ethylene propylene
FF-C-F
F F F |(-C-C-)-(-C-C-)
F F F F
205 16 270
PFA/TFA
Perfluoroalkoxy (R = -C3F7)
F F F O(-C-C-)- (-C-C-)F F F F
260 17 305
ETFE Ethylentetra-fluorothylene
H H F F(-C-C-C-C-)
H H F F
150 25 270
PE Polyethylene H H(-C - C-)
H H
70 31 100
PRE-ANODIZING FOR PAINTING
Pre-anodizing according to GSB.
STANDARD / CERTIFICATE
DIN 17611
MIL-A-8625F Type ?
ASTM B580
AMS-2468
ISO7599
GSB
Custumer specific standards.
Sometimes requirement for COC.
CASE STUDY
Stainless steel, look - high gloss
Can we use Aluminium ?
No Pretreatment -only anodizing for corrosion protection -alloy 1050
Anodic layer
CASE STUDY
Let us develop new visuel surfaces.
Color
NEWS
New color serie: Desert
Tak for opmærksomheden