Electrochemical characterisation speeds up …...prediction of corrosion behaviour E.W. Schuring...
Transcript of 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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Application (PC, OCP, SDM):
Corrosion resistance brazed joints
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
Application (PC, OCP, SDM):
Corrosion resistance brazed joints
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
Application (PC, OCP, SDM):
Corrosion resistance brazed joints
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
Methods for corrosion testing
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
Methods for corrosion testing
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
Methods for corrosion testing
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
Methods for corrosion testing
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)
Methods for corrosion testing
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
Methods for corrosion testing
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 &
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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]
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