Durable offshore wind Corrosion control

AMC Seminar, Den Helder, 3 november 2011

Johan van Malsen

Outline of presentation

TNO

Corrosion

Corrosion control

Research and Development within the DOWES project

Get organised - imlementation in an asset management

syestem

3-11-2011

AMC Seminar

Contract research organisation

Since 1932

Independent

3

Founded by government

4000 employees

Healthy Living

Industrial

Innovation

Defense, Safety

and Security

Energy

Mobility

Built

Environment

Information

Society

Maritime and Offshore

Structures

• Materials (metals, plastics, composites, thermoplasts, thermosets)

• Bonding (adhesives, welding, mechanical bonding)

Influence maritime environment on structures

Environment • Atmospheric

(sun, rain, wind, temperature) • Tidal zone

(wet/dry cycle, aerobic/anaerobic, radiation, temperature)

• Immersed zone (sea water, temperature, pressure, aerobic/anaerobic)

Protection/Mitigation Solutions

• Protective layers • Durable materials • Lubrication • Monitoring

Degradation

• Wear

(abrasion, friction adhesion and

cohesion, erosion, corrosion)

• Chemical degradation

(corrosion, ageing)

• Biological degradation

4-11-2011

Corrosion

(Electro-)chemical degradation of metals resulting in material

dissolution and loss of mechanical strength

Corrosion damage app. 3-5% of GDP, this amounts to 15-25

billion euro’s per annum!

Important contributors to offshore structures degradation:

- General corrosion in sea water

- Microbiological Influenced Corrosion

- Accelerated low water corrosion

- Localized corrosion (pitting, stress corrosion cracking,

corrosion fatigue and hydrogen embrittlement)

3-11-2011

AMC Seminar

Corrosion Control

Corrosion can be controlled by:

Change the medium and environmental parameters

Materials selection; choose more resistant materials

Protection of the materials by a barrier coating

Protection of the materials by (impressed current) cathodic

protection

Dutch Offshore Wind Energy Services

Structures are required to safely operate for over 25 years

Offshore Wind Parks need online monitoring systems for cost

effective maintenance

Development of sensors for remote monitoring of processes

that cause corrosion to offshore structures

Test and validate available sensors

Reduce maintenance costs by modeling degradation

processes

DOWES – TNO workpackage

Coating degradation

Microbiological Influenced Corrosion

Data transfer to DOWES system

Use data in asset maintenance program

Assessment of coatings: Coating Health Sensor

Protection of steel by coatings is based on barrier principle

Change of barrier function can be monitored by means of

electrochemical measurements

Coatings start to degrade long before visual damage can be

observed

TNO offers technology to measure coating degradation before

it can be visually observed

Principle of coating degradation mesurement

Johan van Malsen

Coating Health Monitor

Test set up

3 coating systems based on coating properties

Conventional Electrochemical Impedance Spectroscopy (EIS)

over whole spectrum from 100000 Hz to 0.1 Hz

Measurements with coating degradation sensor at 0.2, 0.5 and

0.9 Hz

Total exposition period 180 days in artificial sea water

Comparison of the results

Results and evaluation

Johan van Malsen

Coating Health Monitor

Comparisson CHM - EIS

coating 1

1.00E+02

1.00E+04

1.00E+06

1.00E+08

1.00E+10

1.00E+12

0.1 1 10 100

exposure time (days)

|Z|

(Oh

m)

black CHM 0.5

black EIS 0.5

Comparisson CHM - EIS

coating 2

1.00E+02

1.00E+04

1.00E+06

1.00E+08

1.00E+10

1.00E+12

0.1 1 10 100 1000

exposure time (days)

|Z|

(Oh

m)

white CHM 0.5

white EIS 0.5

Comparisson CHM - EIS

coating 3

1.00E+02

1.00E+04

1.00E+06

1.00E+08

1.00E+10

1.00E+12

0.1 1 10 100 1000

exposure time (days)

|Z|

(Oh

m)

brown CHM 0.5

brown EIS 0.5

Conclusions so far

The coating degradation sensor is capable of detecting

coating degradation

The actual measurement values are not equal to standard

lab-EIS measurements

Issues that need to be examined:

Electrode tape and adhesion to the coating

Influence of tape on coating degradation

Influence of wetness of the coating

Sensor robustness (i.e. under water installation of sensor)

Battery life

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Microbiological activity sensor

What is microbiological influenced corrosion (MIC)?

Experiment with sensor in artificial sea water

Experiment with sensor in natural sea water and sediment

Experiment with mini mono pile

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What is MIC?

Corrosion initiated or accelerated by micro-organisms

either directly by their metabolic activities or indirectly by

excretion of chemically reactive products.

It has been estimated that as many as 30% of all serious

corrosion events in the industry are influenced by

microbiological activity.

MIC can occur in any system where water is present.

Offshore constructions, piping, ballast tanks, sprinkler

systems.

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When MIC can occur?

Substrate host location to attach

Water no water no MIC

Nutrient no nutrient bacteria can stay in dormant

phase

Oxygen certain types of bacteria need only very small

amounts or no oxygen

More than 99 percent of all bacteria live in biofilm communities

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Microorganisms causing MIC

MIC

Fungi

Methanogens

Organic Acid

Producing Bacteria

Slime Forming

Bacteria

Sulphate Reducing

Bacteria (SRB)

Acid Producing Bacteria (APB)/

Sulphur Oxidising Bacteria (SOB)

Iron/Manganese Oxidising Bacteria (IOB)

Metal-Depositing Bacteria (MDB)

Metal-Reducing

Bacteria (MRB)

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Set-up using Biofilm sensor Experiment-I

Corrosion

coupons

BIOSENSOR

Platinum

electrode

(Redox)

Steel

electrodes

(OCP)

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Experiment I

Artificial sea water, after one week aerobic pseudomona

fluorensens bacteria added

Low sensor signal, redox potential stable, biofilm on

coupons

Anaerobic condition, after 3 weeks Sulphate Reducing

Bacteria (SRB’s) added

Sensor signal up after 2-3 days, redox potential starts

decreasing, when nutrients were consumed, signal

became low

Addition of oxygen by stirring

Reduced SRB activity, Sensor signal low

Anaerobic condition, addition of SRB’s and abundant

nutrients

Sensor signal high

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Set-up using Biofilm sensor Experiment-II

Sediment Natural seawater

BIOSENSOR

OCP measurement Corrosion Coupons

Small minipile

section

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Experiment-II

Natural sea water with sediment, stagnant condition

Development of biofilm, growth tests revealed bacteria

on steel samples, biosensor signal high, after 1 month

activity decreased

3 months later, stagnant condition

Growth tests revealed bacteria, biosensor signal low

and fluctuation. Possible low activity due to lack of nutriens

Nutients were added

Biosensor signal increased and redox potential

dropped. Increased biological activity caused the sensor to

give a higher signal

The redox potential does not influence the sensor signal

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Current plans - Field experiment An experimental set-up that will simulate real-life conditions as closely as

possible, whilst allowing the manipulation of environmental factors)

•Large monopile (already in-house)

•Underwater pH, Oxygen, Salinity, Temp

electrodes (in-house; all continuous

monitoring)

•Redox electrode

•Corrosion coupons

•MIC test kits (SRB and APB)

•Compound electrodes (for OCP

measurements)

•Noise measurement (to check pitting

initiation)

•BIOSENSOR I & 2

•Coating health sensors on outer wall

Get Organised

For effective asset integrity management accurate information

is indispensible

High quality asset inspection data can lead to a cost effective

maintenance program

With a solid maintenance program high cost downtime and

unexpected repair can be prevented

Asset integrity: Design, Inspection, Maintenance