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Protection against microbiological
corrosion and developments in
corrosion detection.
Corina Prent
Contents
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Corrosion
Microbial interaction with iron
Prevention off microbial corrosion
New technology for detecting corrosion
Corrosion
The corrosion process: electrochemical
interaction between a metallic material and
its environment.
Corrosion occurs because of the natural
tendency for most metals to return to
oxidized species in nature in ores.
(Jones, 1995; Groysmann, 2010.
hematite α-FeOOH
The corrosion rate influenced by:
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pH
Temperature
Microorganisms
Type of metal
Presence of surface films (coatings-biofilm)
Mechanical properties (stresses).
B.W.A. Sherar, Corrosion Sci. 53 (2011) 955-960
Microorganism and Iron in a maritime
environment
• Metabolism
• Create a local environment
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Microorganism : Metabolism
Black smokers, deepsea
• Hydrothermal vents:
• Water with 60 °C T< 464 °C
• Depth 5 km
• No light
• Complete ecosystem, based on
iron oxidization?
Microorganism : Metabolism
Titanic wreck:
• Depth: 3000 meter
• Temperature :1–2 °C
• No licht
2010 Halomonas titanicae
Situation:
Local Environment: corrosion
• salt water harbour
• wall thickness 8.8 mm,
• uncoated beneath Low
Water Level and in soil,
• coated above Low Water
Level
Gallionella
Source: TNO, Maritime Materials Performance Centre
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Local Environment: corrosio
Duluth-Superior Harbour
Accelerated Freshwater Corrosion Protection &
Remediation of Structures in Cold Regions
Scribe to bare metal
to simulate impact
Ice Abrasion Samples after Installation
MATERIALS PERFORMANCE October 2008
Microbial corrosion
• Localized aggressive form of corrosion
• Unpredictable  uncontrolled
• Average cost of corrosion is 5% BNP  50% caused by
MIC
• Failures that are of environmental concern or even
hazardous ballast water tanks
A. Heyer at all, Ocean Engineering 70 (2013) 188–200
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Microbial corrosion
Can occur everywere even in:
– Arctic
– Deep sea
Microbial corrosion can also apply to:
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Plastics
Concrete
Coatings
Adhesives
Microbial corrosion
• Requirements:
• Presence of moisture
• Micro-organisms require water to propagate
• Substrate (host location)
• Presence of nutrient
• Nutrients depletion  micro-organisms remain dormant
• Nutrients are restored  microbial growth resumes
• Under aerobic and anaerobic circumstances
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Bacteria involved:
• Slime forming
(e.g. Pseudomonas spp.)
• Sulfate reducing bacteria (SRB)
Pseudomonas
(e.g. Desulfovibrio spp.)
• Acid producing bacteria (APB)
(e.g. Acidithiobacillus thiooxidans)
• Iron oxidising bacteria
(e.g.Acidithiobacillus ferrooxidans)
Patchy biofilm stained with SYTO13
SEM image of SRB
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General mechanism of MIC
• Electrochemical reaction
• Uneven distribution of biofilm  formation of different aeration cells
with anodic and cathodic sites
• Production of corrosive metabolites or may precipitate directly the
metal into the solution
patchy biofilm results in
localized corrosion (pitting corrosion)
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Prevention methods for MIC
1. Change environment
2. Add biocides
Only possible in confined
spaces
3. Pulsing cathodic-anodic protection
4. Generation of protective layer  Biofilm growth
5. Growth inhibition corrosion causing bacteria Anti
microbial
6. Coating
General Causes of coating failures
(new built)
• Surface preparation
• Coating application
• Coating properties
16-09-2010
Causes of coating failures
(during service)
• Degradation due to environmental
effects
• Mechanical damages
• Poor maintenance and cleaning
• Microbial attack
Example Commercial (ballast) tank coating, after 10
weeks of exposure.
Staining of micro-organism around the corrosion pit
FeS
Synthetic seawater
With SRB
16-09-2010
Around the pit
In the pit
Coating degradation by
microorganism
 Biofilms, bacteria can influence the degradation and
consequently the protective properties of the coating.
– By feeding themselves with compounds from the coating.
– By locally changing the circumstances (parameters)on the coating.
 Organisms (can) have different roles in the deterioration
of the coating and in the corrosion attack.
 MID is difficult to predict: living organisms +
imperfections in the coatings.
Humidur by ACOTEC is resistent
against micobial degradation
University of Ghent
16-09-2010
Moscow Eurocorr2010
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Detection
• Sensors for corrosion:
– To late
– To local
• Sensor’s to determine if a biofilm is present
– No discrimination between good en bad film
• Sensors to determine coating degradation
– EIS
• Cumbersome
• Difficult to interpret
• Local measurement
Schematic set-up and analysis
of EIS measurements
Perfecte barrier
coating
Ag/AgCl Ref.
electrode
Pt counter electrode
EIS set up for coating
degradation
measurements
Elektrochemical
processes
occurring
16-09-2010
Moscow Eurocorr2010
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New Principle for easy method
ZRA
E
‘Fingerprinting’
Working electrodes
Reference electrode
Electrolyte
Individual localized processes
A.M. Homborg, Electrochemical Acta, 70 (2012) 199-205
Advantages
‘Fingerprinting’ individual corrosion phenomena at any given
moment in time
Identify and distinguish between different corrosion
mechanisms  passive technique; non-disturbing
Valuable in corrosion monitoring by future fully automated
detection of specific corrosion phenomena
Simplicity of the sensor: Robust, reliable and cheap
Aim
Corrosion type/cause
Corrosion attack
None
Severe
User level
Condition based maintenance
Decision support
Maintainer level
Acknowledgements
• M2I
– Anne Heyer
– Axel Homborg
• TNO
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Fraddy D’Souza/Felipe Leon Morales
Gabriele Ferrari
Job Klijnstra
Gijsbert Strijk
Anouk de Bruin
• 3mE TU Delft
– Arjan Mol
– Hans de Wit
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