Durable offshore wind Corrosion control. AMC Seminar, Den Helder, 3 november 2011 Johan van Malsen

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1 Durable offshore wind Corrosion control AMC Seminar, Den Helder, 3 november 2011 Johan van Malsen

2 AMC Seminar Outline of presentation TNO Corrosion Corrosion control Research and Development within the DOWES project Get organised - imlementation in an asset management syestem

3 3 Contract research organisation Since 1932 Independent Founded by government 4000 employees Maritime and Offshore Healthy Living Industrial Innovation Defense, Safety and Security Energy Mobility Built Environment Information Society

4 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) Degradation Wear (abrasion, friction adhesion and cohesion, erosion, corrosion) Chemical degradation (corrosion, ageing) Biological degradation Structures Materials (metals, plastics, composites, thermoplasts, thermosets) Bonding (adhesives, welding, mechanical bonding) Protection/Mitigation Solutions Protective layers Durable materials Lubrication Monitoring

5 AMC Seminar 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 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)

6 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

7 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

8 DOWES TNO workpackage Coating degradation Microbiological Influenced Corrosion Data transfer to DOWES system Use data in asset maintenance program

9 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

10 Johan van Malsen Coating Health Monitor Principle of coating degradation mesurement

11 Test set up 3 coating systems based on coating properties Conventional Electrochemical Impedance Spectroscopy (EIS) over whole spectrum from 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

12 Z (Ohm) Z (Ohm) Z (Ohm) Johan van Malsen Coating Health Monitor Results and evaluation 1.00E E+10 Comparisson CHM - EIS coating E E+10 Comparisson CHM - EIS coating 2 white CHM 0.5 white EIS E E E E E E+02 black CHM 0.5 black EIS E E exposure time (days) exposure time (days) 1.00E+12 Comparisson CHM - EIS coating E E E E+04 brown CHM 0.5 brown EIS E exposure time (days)

13 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

14 14 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

15 15 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.

16 16 When MIC can occur? Substrate Water Nutrient Oxygen host location to attach no water no MIC no nutrient bacteria can stay in dormant phase certain types of bacteria need only very small amounts or no oxygen More than 99 percent of all bacteria live in biofilm communities

17 17 Microorganisms causing MIC Slime Forming Bacteria Organic Acid Producing Bacteria Sulphate Reducing Bacteria (SRB) MIC Methanogens Acid Producing Bacteria (APB)/ Sulphur Oxidising Bacteria (SOB) Fungi Iron/Manganese Oxidising Bacteria (IOB) Metal-Depositing Bacteria (MDB) Metal-Reducing Bacteria (MRB)

18 18 Set-up using Biofilm sensor Experiment-I BIOSENSOR Corrosion coupons Steel electrodes (OCP) Platinum electrode (Redox)

19 19 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

20 20 Set-up using Biofilm sensor Experiment-II Small minipile section Corrosion Coupons Sediment BIOSENSOR OCP measurement Natural seawater

21 21 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

22 22 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

23 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