ALUMECO – 19-5-2015

Esben Øster

B.Sc.Chem. Eng.

Working whit surface treatment since 1999 at HAI Horsens, Denmark.

10 Years as Quality Manager.

5 Years as Technology Manager.

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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

Cobber containing alloy.Typical 4,0-4,58 % cobber.

20072011201420172024

High strength.Good for cutting.Bad corrosion .Difficult for welding.

BoltsMachine partsHydraulic components

Magnesium containing alloy.

50055754

5005-best anodizing quality.

Facade.Other construction

Magnesium and silicon.

60606012606362626082

High strength.Good for welding.Good for decorative anodizing.

ConstructionWindows Door

Zink containing alloy

7075 Very high stength. CarAeroplaneSpace

A

Rating for different anodizing proces:

WHY SURFACE TREATMENT?

OVERVIEW

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.

Methods• Glass

• Aluminium oxid

• steel

• Sand

•Plastic

CHEMICAL PRE-TREATMENT

Alkaline etch E6Acid etchChemical brightning Elektrolytic 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 GLOSS

Dip proces. Good for complex shape. Whitout current.

Gloss up to ca. 100

Good in combination

whit blastion and

grinding.

Cheapest brighting

method.

CHEMICAL BRIGTNING – HIGH GLOSS

Dip proces. Good for complex shape. Whitout current.

Gloss up to ca. 400.

Good in combination

whit blasting and

grinding.

Containing HNO3. Produce hazard gasses

during 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

Aluksering

Rafbrynjun

Anodisering

Anodizing

Eloksering

Anodisieren

Anodischen oxidation

Hård aluksering Hörd Rafbrynjun Hard Anodizing Hard coat Teknisk 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

Anode

kato

de

kato

de

ANODIC LAYER

LAYER GROWTH

Type II ca. 1/3 Type III ca. ½

Vary from alloy – test.

THE ANODIC LAYER

Layer thicknessDensity – coating veightElements

HARDANODIZING Lower temerature. Change electrolyte. Maybe additive to electrolyte. Longer treating time. Higher current density. Better agitation.

PROPERTIES - HARDANODIZING

Hårdhed Abrasion resistance Corrosion resistance Elektrical insolation Layer thichness Natural color Addition color Heat 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-TREATMENT COLORING

Electrolytic color.

UV resistance.

Few color.

Organic color Not 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 pigment not UV stabile. Indoor Many color

anodic producedoxide layer

anodic producedoxide layer

anodic producedoxide layer

Integral Colouring:

Adsorptive Colouring:

Electrolytic Colouring:

oxide layer with inherent colour

barrier layer

aluminium

barrier layeraluminium

barrier layer

aluminium

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 system

Navn Kemisk navn Kemisk struktur Temp. max.°C

c Smeltepunkt °C

PTFE Polytetra-fluorothylen

F 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

F F-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 / CERTIFICATEA lot of standards for……ask your supplier.

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