Protection against microbiological corrosion and developments in

corrosion detection.

Corina Prent

Contents

• 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: • 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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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

Microorganism : Metabolism

Titanic wreck:

• Depth: 3000 meter

• Temperature :1–2 °C

• No licht

2010 Halomonas titanicae

Local Environment: corrosion

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Gallionella

Source: TNO, Maritime Materials Performance Centre

Situation: • salt water harbour

• wall thickness 8.8 mm,

• uncoated beneath Low

Water Level and in soil,

• coated above Low Water

Level

Local Environment: corrosion

Duluth-Superior Harbour

Accelerated Freshwater Corrosion Protection & Remediation of Structures in Cold Regions

Ice Abrasion Samples after Installation

Scribe to bare metal

to simulate impact

MATERIALS PERFORMANCE October 2008

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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

Microbial corrosion

Can occur everywere even in: – Arctic

– Deep sea

Microbial corrosion can also apply to: – Plastics

– Concrete

– Coatings

– Adhesives

Microbial corrosion

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• 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

Bacteria involved:

• Slime forming (e.g. Pseudomonas spp.)

• Sulfate reducing bacteria (SRB)

(e.g. Desulfovibrio spp.)

• Acid producing bacteria (APB)

(e.g. Acidithiobacillus thiooxidans)

• Iron oxidising bacteria

(e.g.Acidithiobacillus ferrooxidans)

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Pseudomonas

Patchy biofilm stained with SYTO13

SEM image of SRB

General mechanism of MIC

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patchy biofilm results in

localized corrosion (pitting corrosion)

• 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

Prevention methods for MIC

1. Change environment

2. Add biocides

3. Pulsing cathodic-anodic protection

4. Generation of protective layer Biofilm growth

5. Growth inhibition corrosion causing bacteria Anti microbial

6. Coating

Only possible in confined

spaces

General Causes of coating failures (new built)

16-09-2010

• Surface preparation

• Coating application

• Coating properties

Causes of coating failures (during service)

• Degradation due to environmental

effects

• Mechanical damages

• Poor maintenance and cleaning

• Microbial attack

16-09-2010

Example Commercial (ballast) tank coating, after 10

weeks of exposure.

Staining of micro-organism around the corrosion pit

Around the pit

In the pit

Synthetic seawater

With SRB

FeS

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.

16-09-2010 Moscow Eurocorr2010 18

Humidur by ACOTEC is resistent

against micobial degradation

University of Ghent

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

16-09-2010 Moscow Eurocorr2010 20

EIS set up for coating

degradation

measurements

Ag/AgCl Ref.

electrode

Pt counter electrode

Schematic set-up and analysis

of EIS measurements

Perfecte barrier

coating

Elektrochemical

processes

occurring

New Principle for easy method

Individual localized processes

ZRA

Workingelectrodes

Electrolyte

Referenceelectrode

E

‘Fingerprinting’

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 attack

None Severe

Maintainer level User level

Corrosion type/cause

Condition based maintenance

Decision support

Acknowledgements • M2I

– Anne Heyer – Axel Homborg

• TNO

– 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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