Protection against microbiological corrosion and developments in corrosion detection. Corina Prent

Transcription

1 Protection against microbiological corrosion and developments in corrosion detection. Corina Prent

2 Contents Corrosion Microbial interaction with iron Prevention off microbial corrosion New technology for detecting corrosion

3 hematite α-feooh 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.

4 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)

5 Microorganism and Iron in a maritime environment Metabolism Create a local environment 4

6 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?

7 Microorganism : Metabolism Titanic wreck: Depth: 3000 meter Temperature :1 2 C No licht 2010 Halomonas titanicae

8 Local Environment: corrosion Situation: 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 7

9 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

10 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)

11 Can occur everywere even in: Arctic Deep sea Microbial corrosion Microbial corrosion can also apply to: Plastics Concrete Coatings Adhesives

12 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 11

13 Bacteria involved: Slime forming (e.g. Pseudomonas spp.) Sulfate reducing bacteria (SRB) (e.g. Desulfovibrio spp.) Acid producing bacteria (APB) Pseudomonas (e.g. Acidithiobacillus thiooxidans) Iron oxidising bacteria (e.g.acidithiobacillus ferrooxidans) Patchy biofilm stained with SYTO13 SEM image of SRB 12

14 Electrochemical reaction General mechanism of MIC 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) 13

15 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

16 General Causes of coating failures (new built) Surface preparation Coating application Coating properties

17 Causes of coating failures (during service) Degradation due to environmental effects Mechanical damages Poor maintenance and cleaning Microbial attack

18 Example Commercial (ballast) tank coating, after 10 weeks of exposure. Staining of micro-organism around the corrosion pit FeS Around the pit Synthetic seawater With SRB In the pit

19 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 Moscow Eurocorr

20 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

21 Schematic set-up and analysis of EIS measurements Perfecte barrier coating Ag/AgCl Ref. electrode EIS set up for coating degradation measurements Pt counter electrode Elektrochemical processes occurring Moscow Eurocorr

22 New Principle for easy method ZRA E Fingerprinting Working electrodes Reference electrode Electrolyte Individual localized processes A.M. Homborg, Electrochemical Acta, 70 (2012)

23 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

24 Aim Corrosion type/cause Corrosion attack None Severe User level Condition based maintenance Decision support Maintainer level

25 M2I Anne Heyer Axel Homborg Acknowledgements TNO Fraddy D Souza/Felipe Leon Morales Gabriele Ferrari Job Klijnstra Gijsbert Strijk Anouk de Bruin 3mE TU Delft Arjan Mol Hans de Wit 24