Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... ·...

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Electrochemical Methods for Corrosion Behavior Characterization Dr. Patrik Schmutz Head (a.i.) of “Laboratory for Corrosion and Materials Integrity” EMPA ,Swiss Federal Laboratories for Materials Science and Technology Dübendorf, Switzerland contact: [email protected] BioTiNet Workshop Ljubljana, 25 October 2011

Transcript of Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... ·...

Page 1: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Electrochemical Methods for Corrosion

Behavior Characterization

Dr. Patrik Schmutz

Head (a.i.) of “Laboratory for Corrosion and Materials Integrity”EMPA ,Swiss Federal Laboratories for Materials Science and Technology

Dübendorf, Switzerlandcontact: [email protected]

BioTiNet Workshop

Ljubljana, 25 October 2011

Page 2: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Introduction- Corrosion and implant failure- Electrochemistry and implant surfaces

Electrochemical potentiodynamic polarisation - Macroscale characterization of Ti alloys- Local electrochemistry by Microcapillary cell techniques

Electrochemical Impedance Spectroscopy- Measurement principle- Characterization of biodegradable Metallic Mg implants

Crevice and galvanic corrosion investigation- Static and dynamic electrochemical setups- Example of Stainless Steel and Co-Cr-Mo alloys

Conclusions

Outline

Page 3: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Prof. Peter Uggowitzer

• Michael Schinhammer

• Dr. Giancarlo Pigozzi

• Dr. Magdalena

Pawelkiewicz

• Dr. Jörn Lübben

• Dr. Emanuele Cardilli

• Dr. Ngoc Quach-Vu

• Noemie Ott

• Marianne Berg

Swiss Federal Laboratories for Materials Science an d Technology

Laboratory for Corrosion and Materials Integrity

P. Schmutz

Physico-chemistry of reactive metal surface

Dr. Alessandra Beni

Micro- and nanocapillaryelectrochemistry

Dr. Thomas Suter

• Dr. James DeRose

• Dr. Olga Guseva

• Mathias Breimesser

• Aurelien Tournier

Corrosion management

Dr. Markus faller

• Dr. Martin Tuschchmid

• Ronny Lay

• Nikola Gojkovic

• René Werner

• Urs Gfeller

Acknowledgments

Page 4: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Ti alloys

- Corrosion resistant

- Other problems related to fatigue or fretting

Stainless SteelCo – Cr based alloys

- Pitting corrosion

- Crevice corrosion

- Galvanic corrosion

Mg alloys

- Biodegradable

Incr

easi

ng c

orro

sion

res

ista

nce

Decreasing dependence on testing media

Choice of testing solution chemistry

Less relevant

Critical

In - Vitro testing of corrosion processes

P. Schmutz et al., Interface, 17(2), 35-40 (2008)

Page 5: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Hip joints: DLC coating/PE (delamination in vivo, Täger Group)

Ti6Al4V pin implanted in bone (failure

after 6 months due to corrosion

- fatigue)

Cook S.D., et al., The in vivo performances of 250 internal fixation devices:

a follow-up study. Biomaterial, 1987,8; p. 177

Crevice corrosion:

- 90 % of the plates and screws (26 months average)

Example of corrosion related implant failure

Metal

Metal

Me++

Me++ Me++

Me++Me++ + H2O → Me(OH)+ + H+

Cl-

Cl-

Cl-

Cl-

O2O2

Page 6: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

In-vivo evidence of corrosion

Years !!!

Materials development andlifetime prediction

°Accelerate the corrosion process by using more agg ressive media is an alternative but not always possible

°Electrochemical methods are a good alternative

- Very small currents can be measured - It allows earlier detection of on-going degradatio n processes- Corrosion rates are directly linked to electrical charge flow

- There is a very broad range of different informati on can be gained

Requires faster Feedback

Ideally weeks/ month

Accelerated tests and corrosion ?

Page 7: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Micro- and Nanocapillaries:- Local measurements

- Solution analytics

Electrochemical ImpedanceSpectroscopy (EIS)

Electrochemical surface modifications:

- Anodizing- Electropolishing

Thick anodic oxide on Mg

-20

0

20

40

60

80

-2 -1 0 1 2 3 4 5 6

1

2

3

4

phas

e an

gle

log ωωωω

SBF without buffer SBF

log

Z [ ΩΩ ΩΩ

.cm

-2]

Macroscale methods:- Open Circuit Potential

- Potentiodynamic polarization

Dedicated artificial crevice setups:

- Galvanic coupling- Mechanical sollication

Oxidation and

Corrosion

Surface processes and electrochemistry on implants

Page 8: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Setup designed by Dr. Thomas Suter at the Institute for Material Chemistry and Corrosion, ETH Zurich.

Full local electrochemical control for heterogeneous materials characterization

plat

inum

wire

holder

sample

Silicone sealing rubber

d = 300 nm - 1000 µm

elec

trol

yte

brid

ge(S

CE

)

Principle of microcapillary cell

Page 9: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

12 µm

bulk interface

MnS

SEM before

10 -2

10 -1

100

101

102

103

-500 0 500 1000

10 -6

10 -5

10 -4

10 -3

10 -2

Potential [mV] (SCE)

Cur

rent

den

sity

[µA

/cm

2 ]

d area

= 2.5 µm

bulk

MnS

interface

1 M NaCl

Cur

rent

[nA

]

Pitting

Localized corrosion characterization

Stainless Steel : 18Cr/10Ni Electrochemical polarization measurements

Stainless Steel implants

• Plastically deformed and scratched areas are

very susceptible to localized corrosion

Page 10: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Ti alloys and electrochemical Polarization

International standard ISO 10271:2001 (Dental Implants)

Lactic acid solution (pH 2.2)5.85 g/l NaCl + 10 g/l C3H6O3

Ti grade 4 + transfer piece: Ti 6Al 7Nb(b)

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

-0.5 0 0.5 1 1.5

Potential vs. SCE (V)

Log(

i) (A

/cm

^2)

Ti6Al4V SLA

Ti6Al4V SL

(b)

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

-0.5 0 0.5 1 1.5

Potential vs. SCE (V)

Log(

i) (A

/cm

^2)

Ti Grade4 SLATi Grade4 SL

Ti and Ti alloys

• No corrosive attack

under static conditions

• Some ionic release

detected by ICP-MS

Page 11: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Am

plitu

de

E

I

Simple model- for electrochemical Interface

Rs

Rp

CRs : solution resistanceRp : polarization resistance

of the surfaceC: capacitance of the surface

For Mg: Rp= 1000 Ohm/cm 2

Corrosion rate ~ 220 µµµµm/year

Measurement at corrosion potential

Voltage perturbation (10 mV) is applied

- The current response in function of frequency is measured

Ohm’s law gives a simple relation

U = I * R

When AC signal are applied, the relation is

Eac = Iac * Z Z: impedance

EIS: Electrochemical Impedance Spectroscopy

Page 12: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Nyquist plot

Φ

Φ

Z0

Z’

-Z’’

12

EIS: data representation

10 1

10 2

10 3

10 4

10 5

-80

-60

-40

-20

010 -1 10 0 10 1 10 2 10 3 10 4 10 5

Impe

danc

e (O

hm)

Phase (deg)

Frequency (Hz)

Time

Rp

Rs Bode plot

- Frequency dependent representation

Imaginary vs. Real component

Page 13: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Pins

Stents:

weight:4mg

• Magnesium is not only biocompatible... It is animportant element in hundreds of metabolic processes.Suggested daily ratio: 350 mg/day

• Mg-Y-Re alloys are preferred to of AZ91/AZ71.

• A defined degradation sequence during the first3-6 months is aimed at

pH of blood

Mg alloys as degradable implants

Cardiovascular application Osteosynthesis

Page 14: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

• 3 alloys with systematic variation of Y, Zn for screening experiments

• Detailed description of WE43 dissolution

Solutions considered:

• SBF 27 as base (concentration in mmol/l)

100.0 NaCl, 4.0 KCl, 27.0 NaHCO 3, 1.0 MgSO4 * 7H2O, 2.5 CaCl2 * 2H2O, 1.0 KH2PO4, TRIS Buffer (pH 7.4)

• Matrix of solutions with combination of ionic species

In vivo study: very complex media

In-vitroSBF

model solution matrixfor corrosion mechanisms

Alloy Mg Y RE Zr

WE43 Bal. 4.0 3.5 0.5

Alloy Mg Zn Y Ca Mn

WZ21 Bal. 0.9 1.7 0.25 0.15

ZW21 Bal. 2.0 0.8 0.25 0.15

Experimental strategy : alloys and solutions

Page 15: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

-20

0

20

40

60

80

-2 -1 0 1 2 3 4 5 6

1

2

3

4

phas

e an

gle

log ωωωω

SBF without buffer SBF

log

Z [ ΩΩ ΩΩ

.cm

-2]

Immediate immersion of WE43 in SBF 27 with and without buffer agent

• Distinction between uniform or localized corrosion

• Double layer / surface oxide dielectric properties

• Diffusion and adsorption processes can be monitored at low frequency

Reaction rates

localized attack- fast process

Uniform corrosion- slower

Frequency resolved electrochemical impedance measurements allows to characterize reaction mechanisms

EIS: a kind of spectroscopic method

pH 7.4

increased pH

Page 16: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Inductive effects (3) related to ionic adsorption from solution

• Adsorption and Integration of ionic species (inductive effects) can be distinguished from purely growth of hydroxides as a function of time

-Z’’

16Degradation properties of Mg alloys

WE43 in100 mM NaCl (buffered)

-Z’’

1

3

2

Z’

Hydroxide products growth and redeposition

Mg Alloy

Direct Charge transfer

Porous corrosionproducts

(1) (2)

Page 17: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

NaCl, Tris Full SBF

ZW, WZ WE

WE433000

WZ211000

ZW21220

Transition from porous non protecting to more compact corrosion products

Important influence of Yttrium

No significant changes in the nature of the corrosion products

Nature of corrosion products: from ZW21 to WE43

Page 18: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Defective coating model (applicable toother coatings like DLC)

• % of open pores can be determined

• Initial stage of degradation can befollowed as function of time T1 T2 T3

Cor

rosi

on r

ate

Inert Oxide Alloy

Polymermonolayer

Implantation time

2

3

4

5

6

7

8

-2 -1 0 1 2 3 4 5 6

log(f)

log(

Z) 0 h

2 h

10 h

Osteosynthesis application:Thick porous Mg-hydroxides

Electrochemical Impedance Spectroscopy

Intact coating

Solution contact to metal through pores

EIS and porous oxides characterization

Time dependant

Page 19: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Screw:SS, CCM or TiAlNb

SS Plate

Crevice Corrosion

Material combination in implant fixation

Corrosion of metallic implant materials

Stainless steel (SS) is very susceptible tocrevice corrosion problems

Cobalt Chromium Molybdenum (CCM) ismore corrosion resistant but can release“toxic” ionic species when depassivated

FDA concern issued February 2011

Titanium Aluminum Niobium alloys showvery stable passivation but are thanprone to fatigue-corrosion problems,inducing rapid breaking of the implant.

Besides, the intrinsic corrosion problems,dissimilar materials will add the problemof galvanic coupling

Page 20: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Passive layerinstability, active

surface in the crevice

Differential aerationLow migration of OH- ionsincrease of H+ in the crevice

pH decreasesCl- in crevice increases

Galvanic corrosion

Potential differencebetween crevice

and external surfaceincreases

Potential difference betweencrevice and external surface

Crevicecorrosion

Damaged surface

Mechanicaldamage

active surfacein the crevice

Repassivation

Passive film

stabilityC

yclicdam

age

Pas

sive

film

inst

abili

ty

Creviceconditions Dissimilar

materials

Passive layerinstability, active

surface in the crevice

Differential aerationLow migration of OH- ionsincrease of H+ in the crevice

pH decreasesCl- in crevice increases

Galvanic corrosion

Potential differencebetween crevice

and external surfaceincreases

Potential difference betweencrevice and external surface

Crevicecorrosion

Damaged surface

Mechanicaldamage

active surfacein the crevice

Repassivation

Passive film

stabilityC

yclicdam

age

Pas

sive

film

inst

abili

ty

Creviceconditions Dissimilar

materials

Investigation procedure is divided into:

- Static tests- Dynamic tests

Crevice corrosion and galvanic coupling

Page 21: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

FIB cuts: It seems that the first 50 nm above the TiAlV are more or less totally corroded away (not a crack growth)

Si interlayer is very susceptible to crevice corrosion in-vivo

TiAlV

DLC-Si

Si

Nanoscale crevices at coating interface

101 patients DLC/PE101 patients Al 2O3/PE

8.5 year follow-up50% of DLC/PE failed

Page 22: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Cathode½ O 2 + H2O + 2e - = 2OH -

Anode

Me Me2+ + 2e-

Me2+ + 2H2O Me(OH)2 + 2H+

pH

O2

Diff

eren

tial a

erat

ion

e - e -

e -

Cathode½ O 2 + H2O + 2e - = 2OH -

Anode

Me Me2+ + 2e-

Me2+ + 2H2O Me(OH)2 + 2H+

pH

Anode

Me Me2+ + 2e-

Me2+ + 2H2O Me(OH)2 + 2H+

pH

O2

Diff

eren

tial a

erat

ion

e - e -

e -

RE

WE1

WE2

I1 I2 I3

Ch1 Ch3Ch2

Additional cathode Additional cathode

Crevice

RE

WE1

WE2

I1 I2 I3

Ch1 Ch3Ch2

Additional cathode Additional cathode

CreviceAdditional passive panelsto increase differential aeration

Passive or grinded sample in the crevice

Aeration cell:

stabilize the anodic reaction in the crevice ( < 100 µµµµm)

Crevice corrosion and galvanic coupling

All the potential and the currents flowing between electrodes can be measured

Page 23: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

• There is a risk of galvanic incompatibility between SS and CCM especially in case of damaged surfaces

Electrochemical potentials of CCM and SS

Stainless Steel: Cr 17% - Ni 13% - Mo 2.5% - Mn 2% - Fe Bal

CCM: Co 66% - Cr 28% - Mo 6%

9 g/l NaCl, 0.4 g/l KCl, 0.5g/l CaCl2, 0.2g/l NaHCO3

Page 24: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

• Crevice corrosion has been monitored in lactic acid condition and a significant current measured for the coupling SS-SS

• It takes 8 days for localized corrosion to take place and then the current is progressively increasing

• In Ringer’s solution, the environment is too mild to initiate an attack in a reasonable time

Ringer’s solution

Lactic acid solution

Influence of pH on SS surfaces in crevice

Page 25: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

• CCM fully repassivates very fast at low pH (dominating influence of chromium)

• SS is unable to repassivate in crevice conditions• The introduction of CCM in the combination SS-SS increase the risk of

crevice corrosion for the steel

Galvanic current densities

-1.00E-07

0.00E+00

1.00E-07

2.00E-07

3.00E-07

4.00E-07

5.00E-07

6.00E-07

7.00E-07

8.00E-07

0 2 4 6 8 10 12 14 16 18

Time (day)

Cur

rent

den

sity

(A

/cm

^2)

SS(E) Panel

Grinded SS Crevice

Grinded CCM Crevice

CCM(C) Panel

Lactic acid solution

SS – CCM surfaces in crevices

Page 26: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Study under dynamic conditions:

According to ASTM-F75-92

Total Hip Replacement (THR) in 12 sheeps; Euthanasia after 8.5 months

- S. Virtanen, A. Hogson (ETHZ)- B. Von Rechenberg, Tierspital Zürich- S. Mischler (EPFL)

CCM (66% / 28% / 6%)

- Clinical Analysis- Corrosion - Wear

In vivo degradation of CoCrMo hip implants

Page 27: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Dissolution processes studied by ICP-MS

Characterization methods

Static immersion

or

Online Microcapillary flow system coupled to ICP-MS Spectrometer

CCM (66% / 28% / 6%)

Extremely high dissolved ions concentration is found in the tissues next to the implant when micro-motion is present !

Page 28: Electrochemical Methods for Corrosion Behavior ... Workshop Slovenia/BioTiNet_Schmutz... · Electrochemical Methods for Corrosion Behavior Characterization ... -Pitting corrosion

Macro- and microelectrochemical polarization allow to characterize the intrinsic corrosion resistance of materials in aggressive media. The method is ideal in relation with materials development (structure, defects)

Electrochemical Impedance Spectroscopy is the preferred method for a detailed investigation of complex corrosion processes at the OCP. The frequency dependent “spectroscopic information allow to track different corrosion processes (localized, uniform) occurring in parallel on surfaces and coatings

Electrochemical crevice and galvanic coupling setup s are necessary to simulate the aggressive local chemistry that is responsible for most of the implant failures

Dynamic characterization in crevice and galvanic con ditions will be the most relevant electrochemical tests in the case of Ti alloys that are highly corrosion resistant in static conditions (not shown in the webversion)

Leaching of metallic ions that can be investigated by ICP methods is a corrosion related aspect that should not be neglected

Summary and conclusions