Electrochemical characterisation speeds up …...prediction of corrosion behaviour E.W. Schuring...

Electrochemical

characterisation speeds up prediction of corrosion behaviour

E.W. Schuring

J.W. Hooijmans

April 2013

ECN-L--13-034

www.ecn.nl

Electrochemical characterisation

speeds up prediction of corrosion

behaviour

E.W. Schuring

J.W. Hooijmans

Environment and Energy Engineering;

Stand 48

2

• Introduction • Corrosion in real life • Why Electrochemical characterisation of corrosion • Applications

• corrosion resistance coatings • corrosion behaviour (brazed) joints

• Available electrochemical corrosion techniques • Standards • Conclusions

Content

3

Knowledge development:

Degradation processes

Monitoring

Materials

Corrosion in real life

Current status

• Unplanned failures due to

corrosion damage

GDP NL

610 billion euros

Direct annual costs

due to corrosion:

18.3 Billion Euros

(3%)

Early detection of

corrosion phenomena

Materials selection Safety

+ Environment

Knowledge processes

*20-30% reduction could be achieved using existing knowledge.

New technologies enable further reduction.

Barrier quality

4

Corrosion in real life

5

Corrosion mechanisms

Transport of H2O, O2 , NaCl corrosion products etc.

Sufficient corrosion resistant?

C: Barrier properties?

Metal

D: Uniform corrosion

followed by pitting

Me 2+ H2,OH-

Anodic and

cathodic reactions

Uniform corrosion

A: Inter- / trans-

granular corrosion

B: Pitting

• Failure prediction for end-users (more sensitive than

other methods)

• On-site electrochemical characterisation measurements

in tanks and on pipeline coatings

• Determine time dependent quality and barrier properties

of coatings

• Reduce testing time

• Get insight in acting corrosion mechanisms

Too late !!!

Unexpected failure fuel tank

6

Why electrochemicl characterisation? • Standard test methods like salt spray testing are

expensive and need long exposition times • Standard characterisation can lead to

unrightfull acceptance

7

Electrochemical Corrosion testing • Barrier properties

• Corrosion rate

• Time-to-failure prediction

• Sensors

• Development accelerated corrosion test methods

Data fitting Physical model

Re Qcoating

Rcoating Qdl

Rct

Element Freedom Value Error Error %

Re Free(+) 120 N/A N/A

Qcoating-Q Free(+) 1E-07 N/A N/A

Qcoating-n Free(+) 0.89 N/A N/A

Rcoating Free(+) 4800 N/A N/A

Qdl-Q Free(+) 1E-07 N/A N/A

Qdl-n Free(+) 0.4 N/A N/A

Rct Free(+) 0 N/A N/A

Data File:

Circuit Model File: R:\Gouwen\corrosie publiciteit\Model coa

ting.mdl

Mode: Run Simulation / Freq. Range (0.01 - 100000)

Maximum Iterations: 100

Optimization Iterations: 0

Type of Fitting: Complex

Type of Weighting: Data-Modulus

Re Qcoating

Rcoating






Data File:


ting.mdl






Re Qcoating





Data File:


ting.mdl






Z'

-Z''

PC

0 200 400 600

kohm

0

100

200

300

400

500

600

kohm

O2, H2O, Na+, Cl-, etc.

Metaal

Coating of deklaag

O2, H2O Na+,Cl- ,etc.

Na+,OH-Na+,OH- e-e-Fe2+

geleidende

paden

corrosie producten

Fe2+

e-Na+,OH-

corrosie producten

1

2

3

4

Intacte coating

Te laat!!!

Bron: M. Mobin, Malik, A.U., Materials Performance, in February 2005, 2, pp. 28-31. Lekkage olie opslag tank

degradatie

Toenem

ende coatingdegradatie

1

Z'

-Z''

Coating+epox

0 10 20 30 40

kohm

0

10

20

30

40

kohm

2

3

Methods for corrosion testing

Z'

-Z''

PC

0 200 400 600

kohm

0

100

200

300

400

500

600

kohm


Metaal

Coating of deklaag



geleidende

paden

corrosie producten

Fe2+

e-Na+,OH-

corrosie producten

1

2

3

4

Intacte coating

Te laat!!!


degradatie

Toenem


1

Z'

-Z''

Coating+epox

0 10 20 30 40

kohm

0

10

20

30

40

kohm

2

3

Z'

-Z''

PC

0 200 400 600

kohm

0

100

200

300

400

500

600

kohm


Metaal

Coating of deklaag



geleidende

paden

corrosie producten

Fe2+

e-Na+,OH-

corrosie producten

1

2

3

4

Intacte coating

Te laat!!!


degradatie

Toenem


1

Z'

-Z''

Coating+epox

0 10 20 30 40

kohm

0

10

20

30

40

kohm

2

3

8

Stepwise Dissolution Method (SDM) vs Salt spray-BLC

0102030405060708090

100

0,0 0,3 0,6 0,9 1,2 1,5

BLC

aft

er

45

day

s [%

]

Accumulated charge after 6 hours SDM [C]

7075-T6 clad CrO3 anodized - primed material

Application (SDM):

Accelerated Corrosion resistance test coatings

9

Comparison between BLC and SDM – Both show wedging of anodic coating

BLC (45 days) SDM (6 hours)

Embedding mass

Anodic coating

Aluminum substrate

Application (SDM):

Accelerated Corrosion resistance test coatings

Exp

osu

re s

ide

Re Qcoating

Rcoating Qdl

Rct






Qdl-Q Free(+) 1E-07 N/A N/A

Qdl-n Free(+) 0.4 N/A N/A

Rct Free(+) 0 N/A N/A

Data File:


ting.mdl






Re Qcoating

Rcoating






Data File:


ting.mdl






Re Qcoating





Data File:


ting.mdl






Degradation of coating

system over time

Physical interpretation Equivalent circuits

0 10000 20000 30000 40000

-40000

-30000

-20000

-10000

0

Z' Ohm cm2

Z''

Oh

m c

m2

EIS measurements of organic coating

t = 0 hourst = 24 hourst = 100 hourst = 1000 hours

10

Application (EIS):

Corrosion resistance coatings

11

Problem:

Acceptance of brazed joints in heating appliances

Experience:

Brazed joints were accepted after standard corrosion testing, Salt spray testing.

Catastrophic failure in surface due to ‘knife line’-type attack which was not recognised in standard acceptance tests

Result:

User rejects brazed joints in his application(s), although wrong material combinations were originally applied

Consequence:

Limitations in design and optimisation

Solution:

Determine corrosion mechanisms and apply accelerated tests in applicable environments comparing accepted concept and new (brazed) concept

Application (PC, OCP, SDM):

Corrosion resistance brazed joints

12



Potential

Curr

ent

M&G 316L

0 1 2

V

-8

-6

-4

-2

A

Potential

Curr

ent

M&G 316L

-1 0 1 2

V

-8

-6

-4

-2

A

BNi2-solder

AISI316L

AISI316L

BNi5-solder OCP in Chlorinated tap water @ 60°C, aerated

Not recognised in Salt Spray test

AISI316L vs BNi2 AISI316L vs BNi5

13



Coupling tests 316L vs B-Ni 5: Highly electrochemically stressed

Artificial condensate

Aerated @ 60 °C

B-Ni 2 high coupling current

B-Ni 5 very low coupling current

------: B-Ni 2

------: B-Ni 5

AISI316L vs BNi2 + AISI316L vs BNi5

Active behaviour of BNi2 corrosion

time

Curr

ent

Pote

ntial

M&G 316L vs BNi-2 + 316L vs BNi-5

0 20 40 60 80

ks

-40

-30

-20

-10

0

10

µA

-0.2

0.0

0.2

V

0 20 40 60 80

ks

time

Curr

ent

Pote

ntial

M&G 316L vs BNi-2 + 316L vs BNi-5

0 20 40 60 80

ks

-40

-30

-20

-10

0

10

µA

-0.2

0.0

0.2

V

0 20 40 60 80

ks

min

14



0

0,01

0,02

0,03

0,04

0,05

0,06

0,07

0,08

0 5 10 15 20 25

Coulo

mb/c

m2

number of cycles

accumulated Charge [Coulomb/unit area]

BNi-5-condens

BNi-5-Cl-water

las 5-condens

las 1-Cl-water

Test conditions of BNi5 brazed and laser welded joint in AISI316L: - Artificial condensate: Cl-30mg/l; NO3-300mg/l; SO4-50mg/l ( @ 85°C, (5.5h) - Chlorinated tap water: 250ppm Cl @60°C (5.5h)

-0,2

-0,1

0

0,1

0,2

0,3

0,4

0 5 10 15 20 25

OC

P [

Vo

lts]

cycle

OCP (5 min.) after each 15 min SDM cycle

BNi-5-condens

Bni-5-Cl-water

las 5-condens

las 1-Cl-water

Stepwise Dissolution Measurement (SDM) Open Corrosion Potential (OCP)

15


Various method Corrosion measurements: – Corrosion tests to standards (ASTM, ISO; Salt Spray, Stress

Corrosion, Pitting) normally long term testing

– Electrochemical techniques (various conditions): Screening – EIS (Electrochemical Impedance Spectrometry) – ECN (Electro Chemical Noise) – PC (Polarisation Curve) – Couple test Accelerated testing – AAD (Accelarated Anodic Dissolution) – SDM (Step Wise Dissolution Measurement)

16

Corrosion measurement technique

EIS = Electrochemical Impedance Spectroscopy • Sensitive measurement technique

• Data analysis by equivalent circuit modeling

• Determining underlying physical behaviour

• Determine barrier quality in time

• Quick measurement technique (hours)

• Online monitoring possible

Typical for coating systems

Corrosion measurements: EIS


17

Corrosion resistance screening: Electro Chemical Noise = ECN

Electrochemicalinterface

Cell

part

Cell

part

Cell

part

Cell

part

Electrochemicalinterface

Cell

part

Cell

part

Cell

part

Cell

part

E

time or freq. domain

transformation

FFT / MEM

I

detrending

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.10 1.00 10.00

log f [Hz]

Rp

[O

hm

]

Rp high

Rp low

Measurement data;

Potential E + current I

Data analysis Environmental resistance


Low activity

High activity

Comparison method

18

Electro Chemical Noise = ECN

• ECN: potential (=E) and / or current (=I) fluctuations

spontaneously generated by corrosion reactions

• Current flow: magnitude indicates amount of metal loss per unit

time

• Data detrending transformation to freq. or time domain

• Calculation of polarization resistance Rp

• Rp indicator for environmental resistance (the higher the better)

Typical: Comparison materials and material batches Ranking


19

Accelerated Anodic Dissolution (AAD)

Polarization curve; corrosion rate behaviour

Potential

Lo

g (

Curr

ent)

V

A

Anodic reactions Cathodic reactions

OCP

Classic accelerating corrosion

Potential

Lo

g (

Curr

ent)

V

A

E = OCP + ∆E

icorrosion

• extremely high current too aggressive acceleration

• impossible discriminate between subtle corrosion differences

• no correlation with real corrosion mechanism(s)


20

Stepwise Dissolution Method (SDM)

SDM Stepwise Dissolution Measurement

cycle 1

n-th cycle

Method:

OCP monitoring

Potentiostatic polarization; E = OCP + ∆E

∆E = 10 mV to 30 mV

OCP monitoring

Potentiostatic polarization

• Stepwise all relevant corrosion phenomena accelerated

• No change in mechanism only acceleration

Time Results in 7-8 hours

Longer exposure times of days possible

Potential

Lo

g (

Curr

ent)

V

A

1 2 n

i1 i1 in


21

Standards

• Currently no accepted standards, ISO, CEN, ASTM or NEN, are available on electrochemical characterisation

• General applicable standards are:

• ASTM G5 - 13 Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements

• ASTM G61 - 86(2009) Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-Based Alloys

• Standards are under construction/discussion in ISO group TC156 workgroup 11 • NEN workgroup 330040 corrosion revitalised May 2013. Acts as mirror commission

for ISO TC156 • No European TC on corrosion operational

22

Summary corrosion screening method

• ECN method fast; within 1h -1 week results depending on test method!

• Fast pre-selection of promising materials/combinations cost savings • Determining of corrosion initiation

• Determination of corrosion mechanisms and propagation • Life time predictions possible • Strong combination with metallographic post-investigation

• Ranking materials / constructions for corrosion performance

Conclusions

Thanks for your attention &

Please Visit our Stand #48

ECN

Westerduinweg 3 P.O. Box 1

1755 LE Petten 1755 ZG Petten

The Netherlands The Netherlands

T +31 88 515 49 49 [email protected]

F +31 88 515 44 80 www.ecn.nl

Erik Schuring, IWE & Jaap Hooijmans Project leader Materials Testing & Analysis ______________________ ECN T: +31 88 515 4877 | M: +31 6 23455488 e-mails: [email protected], [email protected]

24

Energy-research Centre of the Netherlands

25

Locations

Petten

Amsterdam

Eindhoven Beijing

Wieringerwerf

Brussels

Goirle

26

Ren

ewab

les En

ergy

sav

ings

Supply issues

TRIAS ENERGETICA

Solar

Wind

Biomass

Industry

System innovations

Heat technology

CO2 technology H2&BC’s

ECN

Westerduinweg 3 Postbus 1

1755 LE Petten 1755 LG Petten

T 088 515 4949

F 088 515 8338

[email protected]

www.ecn.nl

Electrochemical characterisation speeds up …...prediction of corrosion behaviour E.W. Schuring...

Documents

Transcript of Electrochemical characterisation speeds up …...prediction of corrosion behaviour E.W. Schuring...