Experimental Study and Modelling of Heat Transfer During Anodizing Of

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Experimental Study and Modelling of Heat Transfer During Anodizing of Aluminum Herman Terryn Vrije Universiteit Brussel (VUB) Research Group Electrochemical and Surface Engineering (SURF) Department Materials and Chemistry, Pleinlaan 2, 1050 Brussels, Belgium Tel:+ 3226293537 (secr 3255) Fax:+3226293200 [email protected] www.vub.ac.be/SURF Part time TUDelft Department of Materials Science and Engineering, Tu Delft Surfaces and Interfaces Group, Corrosion Technology and Electrochemistry Mekelweg 2,2628CD Delft,The Netherlands the SURF brains

Herman Terryn Johan Deconinck

Annick Hubin

Tom Breugelmans Tom Hauffman

8 ZAP members 8 postdoc researchers Iris De Graeve Isabelle Vandendael 25 researchers

Yves Van Ingelgem administrative staff technical staff the SURF brains SURF’s approach

electrochemical and surface processes

combined experimental and modelling approach

experimental techniques modelling techniques

macroscopic and local electrochemical methods reliable parameter estimation by fitting in-situ & ex-situ surface analysis techniques numerical tools for electro-chemical system modelling reactors for electrochemical and surface engineering valorisation of SURF’s research & expertise Closely working with industry industrial partners Anodizing of Aluminium – introduction

Problem: depending on reactor configuration, convection anodizing conditions, ... non-uniform oxide thickness burning effects (high J) process optimisation by trial & error

Improvement: process optimisation based on simulations

Model: Non uniformity comes from T

Anodizing of Al in Wall-Jet set-up Ph.D Tim Aerts "Study of the influence of temperature and heat transfer during anodic oxide growth on aluminium", I.De Graeve & H.Terryn, 2009 -08 | pag. 6 Electrochemical Modelling

• Collaboration with Computational Electrochemistry Group of Johan Deconinck/ Elsyca (spinoff company VUB) • Large project in Flemish community • Based on Boundary Finite Element Calculations • Different electrochemical systems considered – Cases • Gas Production (Cl gas production) • 3 D micro nano electrodes (recovery solutions) • Electroplating mass transfer (Cu, Zn) • Anodizing heat transfer • AC Etching of Al (mass transfer+gas) • Turbulent regime + Two phase systems (fraction of gas)

• Case Anodizing: local heat transfer

Anodizing of Al in Wall-Jet set-up 24-07-08 | pag. 7 Introduction to anodizing - mechanism of porous oxide growth ionic migration through pre-existing film  E ~ 109V / m

thickening barrier oxide

Incorporation of anions see lecture of Shoshan tomorrow Effects of the morphology and composition on the adhesion porous oxide growth Public PhD defence 10/12/2009 | pag. 8 Considered strategy 1) gaining insight on temperature dependency

Heat transfer - Anodizing of Al | pag. 9 Considered strategy 2) modelling of the process

3) simulations of the process

Heat transfer - Anodizing of Al | pag. 10 Anodizing of Aluminium – general introduction Temperature dependency: . Heat production during Anodizing ° Joule heating of oxide ° exothermal oxide formation . Significant influence T on ° electrochemical behaviour ° film morphology ° mechanical properties

° Important influence of heat transfer ° Requirements set-up for validation of simulated experiments: * known convection wall – jet * access to local information electrode reactor * recording different parameters

Anodizing of Al in Wall-Jet set-up 24-07-08 | pag. 11 Wall-jet electrode reactor

a hydrodynamic flow pattern nozzle

fluid at rest potential core

free-jet region H

stagnation zone wall-jet region

z R r

impinged W.E. • Non-uniform convection along electrode  non-uniform hydrodynamical, thermal, diffusion boundary layer

 investigation influence local difference in ht(r), hm(r)

A wall-jet electrode reactor and its application to the study of electrode reaction mechanisms : III. Study of the mechanism of the AC electrolytic grainingAnodizing of aluminium of Al inin Wall hydrochloric-Jet set-up acid, Journal of Applied Electrochemistry, Volume: 28, pp: 387 - 396, 1998, Laevers P., Hubin A., Terryn H., 24-07-08 | pag. 12 Vereecken J. Wall-jet electrode reactor experimental set-up

jet central circuit nozzle column

electrode cell overflow sample holder temperature control electrolyte supply

electrolyte drain reservoir

A wall-jet electrode reactor and its application to the study of electrode reaction mechanisms : III. Study of the mechanism of the AC electrolytic grainingAnodizing of aluminium of Al inin Wall hydrochloric-Jet set-up acid, Journal of Applied Electrochemistry, Volume: 28, pp: 387 - 396, 1998, Laevers P., Hubin A., Terryn H., 24-07-08 | pag. 13 Vereecken J. Wall-jet electrode reactor experimental set-up sample holder & sample

sample holder piston

A wall-jet electrode reactor and its application to the study of electrode reaction mechanisms : III. Study of the mechanism of the AC electrolytic grainingAnodizing of aluminium of Al inin Wall hydrochloric-Jet set-up acid, Journal of Applied Electrochemistry, Volume: 28, pp: 387 - 396, 1998, Laevers P., Hubin A., Terryn H., 24-07-08 | pag. 14 Vereecken J. Wall-jet electrode reactor experimental set-up PVDF-core (diameter  = 40mm) with 5 thermo-couples TT electrical contact ring ( ring =  sample)

1 2 3 4 5

= 40mm

-15 -10 0 +5 +15 mm

Distance from centre of sample (mm) • local measurement T on electrode • electrochemical quantities i (j),U • flow rate, temperature of electrolyte

A wall-jet electrode reactor and its application to the study of electrode reaction mechanisms : III. Study of the mechanism of the AC electrolytic grainingAnodizing of aluminiumof Al inin Wall hydrochloric-Jet set-up acid, Journal of Applied Electrochemistry, Volume: 28, pp: 387 - 396, 1998, Laevers P., Hubin A., Terryn H., 24-07-08 | pag. 15 Vereecken J. Microhardness,wear, porosity 20 µm anodized film in H2SO4 17 V

Influence of the anodizing temperature on the porosity and the mechanical properties of the porous anodic oxide film, Surface Science and Technology, Volume: 201, N° in volume: 16-17, pp: 7310 - 7317, 2007, Aerts T., Dimogerontakis T., De Graeve I., Terryn H., Fransaer J Wall-jet electrode reactor hydrodynamic flow pattern

Flow field near W.E. (Re = 600) Evolution of hT in function of radial position

80000 Re = 500 70000 Re = 5000

60000

50000

40000 (W/m²/K)

T 30000 h

20000 height height (m)

10000

0 0 0.005 0.01 0.015 0.02 Radial position (m) Radial position (m) Known conditions of convection and heat transfer Quantitative approach possible !

Anodizing of Al in Wall-Jet set-up 24-07-08 | pag. 17 Influence of variation of local temperature during Scope anodizing* ** Wall jet reactor hT in function of radial position

heat transfer ↑ Re = 500 Re = 5000 . Re = 500 256C/dm² Re = 5000 (W/m²/K)

heat transfer ↓ T h . Re = 5000 256C/dm² Re = 500

Radial position (m) Effect noticeable ° electrochemical behaviour ? ° microstructure oxide ?

Anodizing of Al in Wall-Jet set-up 24-07-08 | pag. 18 Influence of variation of local temperature during anodizing Experimental conditions

AA 1050

Alkaline etched + desmutted

DC – anodizing in 145g/l H2SO4 + 5g/l Al2(SO4)3.18H2O

galvanostatic anodizing 1  16A/dm² - 25, 45°C - 512C/dm²

Electrolyte flow rates Re = 500  5000

Anodizing of Al in Wall-Jet set-up 24-07-08 | pag. 19 Demonstration influence heat transfer - electrochemical behaviour local electrode temperatures

Re = 800

higher T(r,t) towards border electrode

in correspondence heat transfer

similar evolutions at other Re for comparison: T( r, tfinal )

ExperimentalPublic study PhD defenceand modelling10/12/2009 of anodizing of aluminium in a wall-jet electrode set-up in laminar and turbulent regime, Corrosion Science, | pag. 20 Volume: 51, N° in volume: 7, pp: 1482 - 1489, 2009, Aerts T., De Graeve I., Nelissen G., Deconinck J., Kubacki S., Terryn H Influence of variation of local temperature during anodizing galvanostatic 8A/dm² 45°C Re= 500  5000

TW.E.(r, t) UW.E.(t)

effect ° immediate ° moderate but measurable

Anodizing of Al in Wall-Jet set-up 24-07-08 | pag. 21 Influence of variation of local temperature during anodizing galvanostatic 8A/dm² 45°C Re= 5000  500

UW.E.(t) TW.E.(r, t)

effect ° immediate ° moderate but measurable

Anodizing of Al in Wall-Jet set-up 24-07-08 | pag. 22 strategy of the thesis 1) gaining insight on temperature dependency

Public PhD defence 10/12/2009 | pag. 23 Demonstration influence heat transfer - electrochemical behaviour

doxide (r) Telectrode (r, tfinal)

• reduced convection  less uniform electrode • incline from centre towards border

influence heat transfer on anodizing:

heat transfer ↓  DTelectrode (r) ↑ doxide (r) ↑ where Telectrode (r) ↑

convection uniform anodizing process

ExperimentalPublic study PhD defenceand modelling 10/12/2009 of anodizing of aluminium in a wall-jet electrode set-up in laminar and turbulent regime, Corrosion Science, | pag. 24 Volume: 51, N° in volume: 7, pp: 1482 - 1489, 2009, Aerts T., De Graeve I., Nelissen G., Deconinck J., Kubacki S., Terryn H Demonstration influence heat transfer - strange observation local oxide thickness doxide (r) local electrode temperature

incorrect measurement ? no: burning

Public PhD defence 10/12/2009 Study of initiation and| pag. development 25 of local burning phenomena during anodizing of aluminium under controlled convection, Electrochimica Acta, Volume: 54, pp: 270 - 279, 2008, Aerts T., De Graeve I., Terryn H Local phenomena: burning - oxide morphology normal oxide burning area

“oxide hillocks”

Public PhD defence 10/12/2009 Study of initiation and| pag. development 26 of local burning phenomena during anodizing of aluminium under controlled convection, Electrochimica Acta, Volume: 54, pp: 270 - 279, 2008, Aerts T., De Graeve I., Terryn H Local phenomena: burning - burning area oxide morphology

oxide hillocks: •base  normal pores •top  tubular structure

characteristic for burning Public PhD defence 10/12/2009 Study of initiation and| pag. development 27 of local burning phenomena during anodizing of aluminium under controlled convection, Electrochimica Acta, Volume: 54, pp: 270 - 279, 2008, Aerts T., De Graeve I., Terryn H Local phenomena: burning - burning area oxide morphology

tubular structure

transition

normal structure

quenching of burning

Public PhD defence 10/12/2009 | pag. 28 Local phenomena: burning - general evolution pore

development

healing

Public PhD defence 10/12/2009 | pag. 29 Influence of electrode temperature

Traditional approach: varying Telectrolyte

• TAl ?

. in-situ measurements

. calculations (CFD)

 uncontrolled …

Public PhD defence 10/12/2009 | pag. 30 Influence of electrode temperature

presented approach: varying applied Tanode

• TAl known and controlled

realized by in-house developed electrode holder

Public-Anodizing PhD defence of aluminium 10/12/2009 under applied electrode temperature: process evaluation and, Surface & Coatings Technology, Volume: 204, pp: 2754 - 2760,| pag.2010, 31 Aerts T., De Graeve I., Terryn H.Jet set-up 24-07-08 | pag. 31 Temperature applied anodizing T-controlling sample holder(s) Water cooling Al heat sink

Anodizing of Al in Wall-Jet set-up HeatControl transfer of the - Anodizingelectrode of temperature Al for electrochemical studies: A new approach illustrated on porous anodizing of aluminium, 24-07-08 | pag. 32 Electrochemistry| pag. 32 Communications, Volume: 11, pp: 2292 - 2295, 2009, Aerts T., De Graeve I., Terryn H. Influence of electrode temperature – electrochemical behaviour T vs. T anodizing @ 1 A/dm² : Al H2SO4

TH2SO4 =effect 25 °C TAl > effect TH2SO4 • electrode potentials • oxide thickness & morphology • anodizing ratio ionic migration

ComparisonPublic between PhD defence the influence10/12/2009 of applied electrode and electrolyte temperatures on porous anodizing of aluminium, Electrochimica Acta, Volume: 55,| pag.pp: 395733 - 3965, 2010, Aerts T., Jorcin J., De Graeve I., Terryn H. Comparison between the influence of applied electrode and electrolyte temperatures on porous anodizing of aluminium, Electrochimica Acta, Volume: 55, pp: 3957 - 3965, 2010, Aerts T., Jorcin J., De Graeve I., Terryn H. Results – modelling of the process proposed , optimized model : hc,0 = 53.0 V

B1 = -0.09823 V/K where Jc,0 = 5.971e-8 A/m² -1 B2 = 0.06957 K

experiments

 good correspondence  in wide range of conditions: • 86 % : |Dh|  0.5 V • 30 % : |Dh|  0.1 V

Public PhD defence 10/12/2009 | pag. 35 Considered model Hydrodynamics solution   .v  0  + turbulent viscosity from low-Re k-w model  v          v..v    2v  p  t  temperature distribution  T      cp,i i   vi ..T   .iT  Qi i=electrolyte or Al  t 

QAl  QOhmic  Qloss  Qanod

  Al . j² SDT h j

Anodizing of Al in Wall-Jet set-up 24-07-08 | pag. 36 Considered model Electrical potential distribution     j   U i=electrolyte or Al . iU i  0 i i i

Anodizing boundary condition (still working on this) empirical equations Or Physical equation (High Field equation) B  zFh 1 zFh  D = 9.86E-6 j  D.T m .e T .e RT  e RT  with B = -2600   α = 0.0116   z = 3 and m = 0.5

Oxide thickness M. j.Dt j(r) d  . (Faraday) ox z.F.

Anodizing of Al in Wall-Jet set-up 24-07-08 | pag. 37 Anodizing - experiments vs. model Followed approach

consider ° Wall-jet reactor set-up

° TH2SO4 T(r,tf)EXP - dox(r,tf)EXP ° Rea ° j - Q

simulation of anodizing process T(r,tf)NUM - dox(r,tf)NUM

? T(r,tf)EXP T(r,tf)NUM ? dox(r,tf)EXP dox(r,tf)NUM

Modelling of the porous anodizing of aluminium: Generation of experimental input, Surface Coatings Technology, Volume: 205, pp: 4388 - Anodizing of Al in Wall-Jet set-up 4396, 2011, Aerts T., Tourwé E., Pintelon R., De Graeve I., Terryn Hnce 10/12/2009 24-07-08 | pag. 38 | pag. 38 experiments vs. model Numerical T(r,tf)

This image cannot currently be displayed. 4A/dm² This image cannot currently be displayed. 8A/dm²

Modelling of the porous anodizing of aluminium: Generation of experimental input, Surface Coatings Technology, Volume: 205, pp: 4388 - 4396, 2011, Aerts T., Tourwé E., Pintelon R., De Graeve I., Terryn Hnce Anodizing1 of Al in Wall-Jet set-up 24Experimental-07-08 | pag. study 39 and modelling of anodizing of aluminium in a wall-jet electrode set-up in laminar and turbulent regime, Corrosion Science, Volume: 51, N° in volume: 7, pp: 1482 - 1489, 2009, Aerts T., De Graeve I., Nelissen G., Deconinck J., Kubacki S., Terryn H0/12/2009 | pag. 39 Simulations of the process - TH2SO4 = 25 °C - j = 4 A/dm² - Rea = 5000 This image cannot currently be displayed. resultsThis image cannot currently be displayed.

• Mutech model > reference model

• good correspondence Mutech exps  offset error remains  behaviour near border

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http://www.elsyca.com/ Model equations DV I _ + Laplacian equation for ohmic drop in electrolyte - + + - - • Electrical field: E =-grad U=- U + - + + - + • Current density: J = s.E = - s . U - + -

• Charge conservation:div J = 0 => .(U) = DU = 0

U(x,y,z) Boundary conditions

• Anodic polarisation : Jn = f (h) = f (V - U) 1 1 h • Cathodic polarisation: Jn = f2 (h) = f2 (V - U) V(x,y,z)

• Insulating walls / electrolyte meniscusJn : = 0

42 Case A: high density caliper part load

This image cannot currently be displayed. No anode Flight bar Top View shielding This image cannot currently be displayed.

120 parts per rack / flight bar

43 Case A: high density caliper part load

Imposed DV I main [A] / Imposed DV I aux [A] / Porous layer thickness Dt [min] main [V] flightbar aux [V] flightbar 40 12.9 877 N/A N/A

This image cannot currently be displayed. Average value

This image cannot currently be displayed. 14.4 [micron]

Minimum value 10.9 Maximum value 19.9 Standard 1.8 deviation Minimum 12.0 specification Maximum 18.0 specification