Presentation of various pretreatment methods for Aluminum

Presentation of various pretreatment methods for AluminumAutomotive Cycle

Mark Wolf, PWT/VFT, Bad Nauheim, 17.April.2012

Pretreatment of Aluminium | Mark Wolf PWT/VFT | 17.April.20122

Pretreatment of AluminumAgenda

•Whey is a pretreatment of aluminum surfaces necessary?

•Aluminum pretreatment process chain

•Pretreatment methods of Aluminum

•Worldwide Local sourcing

•Abstract


Pretreatment of Aluminum

Whey is a pretreatment of aluminum surfaces in regard to the used joining technique necessary?

• The aluminum oxide layer does have an high influence in quality of joinings

- Adhesive bonding : long-term durability of boning (bond line corrosion)

- Arc welding (MIG welding): start of weld arc, process stability of welding arc (position of welding seam)

- Spot welding: process stability, wear of welding tip

• For thermal joining techniques the aluminum surface have to be lubrication free to achieve a high quality joining. (porosity, hydrogen embrittlement)

Adhesive bonding Laser fillet weld

beölte

Einflus Al-Vorbehandlung [ AC 120 ]

31,0 34,0

33,0

4,00

5

10

15

20

25

30

35

Entfettet Gardoclean 299

Zugs

cher

span

nung

[ M

Pa ]

ungealtert SST 3000h


Pretreatment of Aluminum Process chain

Process chain

Before adhesively bonding aluminum • To remove fouling, grease and oil

• To establish a defined oxide layer • To activate the surface• To enhance resistance to aging on

bonding layerBefore welding aluminum

• Surface free of dirt and grease• Defined oxide layer thickness• Uniform volume and

contact resistance

When reworking aluminum • Extraction systems not designed for

oil-laden grinding swarf • In some cases better surface finish

evaluation when surface is clean

Pre-treatment of Al pressings

Bodyshop

Finishing/paintshop

Press shop

Reasons for carrying outaluminum pre-treatment


Pretreatment of Aluminum Pretreatment methods of Aluminum

Single part pretreatment:

• Facility:- in dipping bath- Continuous pretreatment

• Raw products:- Stamping parts- Casts- Extrusion

• Logistics:- Special racks- Additional handling

Local pretreatment:• Facility:

- In body shop cell

• Raw products:- Stamping parts no

stamping oil- Casts- Extrusion

• Logistics:- Additional handling in body

shop

Coil pretreatment:• Facility:

- Coil coating

• Raw products:- Coil metal

• Logistics:- No additions process

Defined oxide layerAnti-corrosion oil

Aluminum

Ti/Zr


Pretreatment of Aluminum single part pretreatment

Chemetall Gardoclean 299/4 (Si)Chemetall Gardoclean 299/4 (Si)

Force drying100°C, 20 min

Pre-degreasing / passivation80-85°C, 12 min, pH 10-12

Degreasing / passivation80-85°C, 12 min, pH 10-12

Rinsing ID.I. water

Rinsing IID.I. water

Rinsing IIID.I. water

Henkel Alodine 2040 (Ti)

Rinsing IVD.I. water

Degreasing I55-60°C pH 9.5-11

Rinsing IIndustrial water (non-drinking)

Degreasing II55-60°C pH 9.5-11

Deoxidizing Alodine 2040 (Ti)35-40°C pH 1.2-1.5 Tif

Rinsing VD.I. water

Rinsing VID.I. water

Rinsing IIIndustrial water (non-drinking)

Rinsing IIID.I. water

Force drying100°C

Gardoclean 299/4:• Compatible with all joining

techniques • Short process• No stainless steel racks

Alodine 2040:• Compatible with all joining

techniques• Best surface cleaning • Best surface insulation

resistance

Conclusion:• Best system for stable

body shop processes• High cost


Pretreatment of Aluminum Coil pretreatment

Method for pretreatment of coils

Defined oxide layer

Al supplier Press shop Body-shop

Ti/ZrAnti-corrosion oil Deep-drawing compound

Aluminum

Adhesive

Process flow for aluminum pretreatment


Pretreatment of Aluminum Coil pretreatmentTiZr conversion coating for semi structural bonding:

• Temporary corrosion protection (predominantly Zr)

• Prevention of re-formation of oxide layer

=> same surface resistance as before (for the moment) (predominantly Ti)

=> improved weld ability

• Produced by Chemetall as Gardobond X 4591

• At most European supplier available

• Risk of read-through after Zink phosphate bath in paint shop

Defined oxide layerAnti-corrosion oil

Deep-drawing compoundAdhesive

Aluminum

Ti/Zr


Pretreatment of Aluminum Coil pretreatment Anodized layer

Anti-corrosion oilDeep-drawing compound

Adhesive

Aluminum

Thin anodized film for structural bonding:In the anodizing methods, the aluminum surface is cleaned and the natural aluminum oxide layer removed. Then a defined, firmly adhering oxide layer is built up, consisting of a thin barrier layer, only a few nm thick and free of pores, and a porous surface film.

•Description of the method:

- Degrease/de-oxidize (acidic)

- Anodize

•Patent bended

•Special equipment is necessary

•No spot-welding


Pretreatment of Aluminum Coil pretreatmentOxsilan MM 0705 conversion coating

for structural bonding: • Same application equipment as TiZr Coating

• Same high level performance after aging like TAF Coating

• No patent bending for oxsilan application at aluminum supplier

• No marking in paint shop after Zink phosphate bath

• Spot-welding possible

Defined oxide layerHotmelt

Adhesive

Aluminum

Oxsilan


Pretreatment of AluminumLocal pretreatmentPlasma pre-treatment:

• Burn off lubricants

• Activate the surface

Laser pre-treatment : • Burn off lubricants

• Micro structure of surface

Conclusion:• Local pretreatment no on stamping parts

(Stamping oil)

• Potential for castings and extrusion for welding

• No potential for structural bonding with actual technology Quelle: CleanLaser

Quelle: PlasmaTreat

Undefined oxide layerAnti-corrosion oil

Drawing oil

Press shop Bodyshop

Adhesive

Aluminum


Pretreatment of AluminumWorldwide Local sourcingEurope:

• Pretreatment of aluminum in Europe available

Rest of world:• Pretreatment not available ,

no standard process at local OEM’s

Conclusion:• World wide production of aluminum structure in body in white needs new sources for

aluminum pretreatment.

• New logistic concepts has to be developed

Single part pretreatmentGardoclean 299/4

Single part pretreatmentAlodine 2040

Coil pretreatmentTAF

Coil pretreatmentTiZr / Oxsilan

Deutschland (Europa)In house Suppliers

Suppliers NovelisNovelis, Hydro, Aleris, Alcan

Süd Afrika In house

China In house Kobe-Steel

USA Fa. Novelis


Pretreatment of AluminumAbstract

• Pretreatment of Aluminum is necessary for good joining quality and stable processes

• Depending on the joining technique and material process chain, different pretreatments are necessary.

• For sheet, metal coil pretreatment is the most economic method.

• Worldwide Local sourcing of pretreated aluminum is difficult. Therefore new sources have to be established and new logistic concepts have to be proven.


Thank You

Presentation of various pretreatment methods for Aluminum

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