Anodizing of high alloyed aluminum alloy group: Al-Cu Common alloy: EN AW 2024 Medium-High strength material Excellent shape stability Age-hardened and stress-relieved Low corrosion

1 © PIPPIG-SCHMID Aluminium + Oberflächen

Anodizing of high alloyed

aluminum

Kristin Pippig-Schmid

Dirk Hüwelhans

IHAA 16th Technical Symposium, October 5-7, 2016


2000 alloy group: Al-Cu

Common alloy: EN AW 2024

Medium-High strength material

Excellent shape stability

Age-hardened and stress-relieved

Low corrosion resistance

High temperature applications

Field of application: aerospace, machining industry,

injection molding (plastic industry)

Technical Anodizing: Poor (limited oxide layer thickness)


7000 alloy group: Al-Mg-Zn

Common alloy: EN AW 7075, EN AW 7022

High-strength materials: TYS = 460 – 540 MPa

Very good shape stability

Age-hardened and stress-relieved

Trend to stress corrosion cracking

Excellent machinability

Field of application: Aerospace, Machining industry,

Automotive

Technical Anodizing: Medium-Good


Anodizing of medium and high strength material with

copper amount > 2.5% and silicon amount >7% is critical

in standard anodizing processes.

Problematic: Intermetallic phases, electrical conductivity,

partly overheating

Trend of material “burning” at anodizing process

Trend of dissolving during process


3 kinds of interaction of

intermetallic phases in oxide layers

Integration, Oxidation, Dissolution

Si – trend to integration

Cu (e.g.CuAl2), Mg (e.g.β-AlMg) –

trend to dissolution and oxidation

Fe (e.g.α-AlFeSi) – trend to dissolution

and integration

→ Discontinuity of oxide layers

→ Influence on oxide layer quality

→ Influence on anodizing process


800x (Alloy EN AW 6061, plate)

Anodizing of high alloyed aluminum – Part 2

Motivation / Idea / Company

Surface Treatment is our passion.

Two companies – Two characters – One passion

20 years of 20 years of

experience in experience in

- Equipment manufacturing - Anodisation

- Metallic coatings (Cr, Ni…) - Testing

- Anodisation - Conversion layers

- Ceramic layers - Bonding

- Paints

►A lot of project ideas wait of realization.

We are open for discussion, you welcome to share.

© PIPPIG-SCHMID Aluminium + Oberflächen

Anodizing of high alloyed aluminum - Project

Motivation

Generate an anodizing process to produce thick oxide layers

and optimize the layer quality of high copper and

silicon alloyed aluminum.


Anodizing of high alloyed aluminum - Project

Project task (first step)

Development of an efficient anodizing process:

► high deposition rate (4-6µm/min)

► current density 7-10A/dm2

► short process time

► handling at room temperature

► avoiding complex process bath composition

Development of a manufacturing equipment concept

First process runs: anodizing of two high Cu-alloys EN AW

2024 (ca.4% Cu) and EN AW 2219 (ca.6% Cu)


EN AW 2024 T351 – AlCu4Mg1

Good machinability

No weldability

Poor corrosion resistance

High strength at high temperatures

Rm 400-440MPa, A50 7-14% (depend on plate dimension)

Application area: High dynamic and static stressed parts

Machining industry, Aerospace


Si Fe Cu Mn Mg Cr Ni Zn Ti Pb

Max.0.5%

Max.0.5%

3.8-4.9%

0.3-0.9%

1.2-1.8%

Max.0.1%

- Max. 0.25%

Max. 0.15%

-

Alumold® 350/Tempral EN AW 2219 T851 - AlCu6Mn

Poor corrosion resistance

High-temperature applications (service temperature up

to 180°C)

Excellent machining / Easy to polish

Good weldability

Application area: rubber molding, reactive molding, blow

molding or composite material forming, plastic industry


Si Fe Cu Mn Mg Cr V Zn Ti Zr

Max.0.2%

Max.0.3%

5.8-6.8%

0.2-0.4%

Max. 0.02%

Max.0.1%

0.05-0.15%

Max. 0.1%

0.02-0.1%

0.1-0.25%


Anodizing of high alloyed aluminum –

Anodisation process

Mechanical pre treatment

Chemical pre treatment

Anodisation

Coloring

Adsorptive Coloring Elektrolytical Coloring

Sealing

Optional

Degreasing, Etching,

Neutralization

Rinsing steps in between

each process step



Coating characterisation EN AW 2024

Uniform oxide layer

Coating Thickness: 40-45µm




Partly Integration and Oxidation of

intermetallic phases in oxide layer.

Displace and movement of coppery

phases during anodizing.




O-K Mg-K Al-K Si-K S-K Cl-K Ca-K Mn-K Fe-K Cu-K

Base(3)_pt1 37.16 0.19 48.70 6.12 5.62 2.22 Base(3)_pt2 43.30 0.44 37.28 12.15 3.22 0.73 0.31 2.56 Base(3)_pt3 0.63 90.60 1.18 1.18 6.41 Base(3)_pt4 1.20 1.85 92.07 0.48 4.41 Base(3)_pt5 53.56 0.51 38.26 0.40 6.34 0.94




Dissolution of intermetallic

phases in oxide layer.

Uniform oxide layer

Coating Thickness: 40-45µm




Al-K Cu-K

Base(2)_pt1 53.05 46.95

CuAl2 phase




O-K Al-K S-K Mn-K Cu-K

Base(1)_pt1 94.29 0.68 5.03

Base(1)_pt2 94.58 5.42

Base(1)_pt3 94.38 5.62

Base(1)_pt4 95.32 4.68

Base(1)_pt5 52.06 41.52 6.42

Base(1)_pt6 53.14 40.10 6.76

Base(1)_pt7 94.77 5.23

Anodizing of high alloyed aluminum

Summary

- Characterisation of oxide layers

- Uniform oxide layer thicknesses

of high Cu-alloyed aluminum possible.

- High deposition rates and avoiding of

“burning” effects with equipment adaptation controllable

Further project steps

- Coating optimization (better integration of large phases)

- Adaptation of deposition rates

- Easy implementation in existing production lines

- Functional tests (abrasion, corrosion…)

► Looking for a project cooperation partner


Material support by Constellium Sierre:

A big Thank You!

Thank you for your attention.

Questions


Documents

Anodizing of high alloyed aluminum alloy group: Al-Cu Common alloy: EN AW 2024 Medium-High strength material Excellent shape stability Age-hardened and stress-relieved Low corrosion