Microbial influence on

corrosion of copper in the

repository environment

Copper corrosion seminar, 15.12.2016

Aalto University, Otaniemi

Leena Carpén, Pauliina Rajala, Elina Huttunen-Saarivirta,

Maija Raunio, Malin Bomberg

VTT Technical Research Centre of Finland Ltd

Place for a photo

(no lines around photo)

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What is microbial corrosion?

Corrosion can be defined as the degradation of a material due to a

reaction with its environment

MIC = Microbially or microbiologically induced or influenced corrosion

Microbes or their metabolic by-products induce changes in chemical or

physical conditions

Microorganisms are able to accelerate several types corrosion such as:

general corrosion

localized corrosion

pitting and stress corrosion cracking

Anode:

M Mn+ + ne-

Cathode:

O2 + 2H2O +4 e- 4OH- or

2H+ + 2e- H2

Image: Mari Raulio

319/12/2016 3

Why to study MIC?

In oxygen-free water, the corrosion rate of steel and copper is low,

unless the water is very acidic or there is microbiological activity in the

environment

The groundwater contains up to 105 microbial cells mL-1 with

considerable species diversity

Microorganisms may significantly contribute to corrosion

by producing corrosive metabolic products

by consuming oxygen

by forming discontinuous accumulations

by oxidising iron(II) ions to iron(III) ions or manganese(II) to manganese(IV)

ions or ammonia to nitrites

by accelerating the electrochemical part reactions

The aim is to characterize biofilms associated with corrosion and the

ability of indigenous groundwater microbes to produce corrosive agents

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What is biofilm?

The activity of microorganisms attached to the

surfaces and the properties of formed biofilms

are essential factors when considering the

possibility of microbially induced corrosion

In aquatic environments microorganisms attach

to surfaces and form multispecies biofilms

Microbial cells in a biofilm differ from free living

cells of the same species

Formation of extracellular polymeric substances

(EPS) = slime

Under the biofilm the conditions may differ

remarkably from the surrounding solution

”Mushroom” model of biofilm

Center for Biofilm Engineering

Image: Mari Raulio

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Microorganisms associated with MIC

• Sulphate reducing bacteria, SRB (Desulfovibrio, Desulfobacter,

Desulformaculum) and Iron reducing bacteria (Pseudomonas)

• Sulphur oxidizing-bacteria (Thiobacillus)

• Organic acid producing bacteria (Clostridium)

• Manganese- and iron-oxidizing bacteria, MFOB

(Gallionella, Sphaerotilus, Leptothrix, Crenothrix)

• Manganese depositing bacteria (Bacillus, Pseudomonas, Micrococcus)

• Slime-forming bacteria (Bacillus, Flavobacterium, Sphaerotilus)

• Methane producers

• Acid producing fungi

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MIC

Not all microbes are corrosion inducing

Some might promote passivation of the surface

Majority of microbes do not have any effect on corrosion

Biofilm formation is key step for initiation of corrosion

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Corrosion in deep bedrock

Copper

Microbial activity may have an affect on the integrity of copper

capsule

Microbial metabolites may enable the stress corrosion cracking

or cause general or localized corrosion

Challenge is to identify the key microbial processes in each

phase of the repository

Aggressive agents for copper

Acetate, (nitrate), nitrite, ammonium, sulphide and organic acids

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Corrosion in deep bedrock

Copper

Native microbes form biofilm on surfaces

Distinct corrosion products when microbes are present

copper(I) sulfide deposit vs. copper(I) oxide

Carpén et al. ICC N-0-17 2014

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Results from our studies

MICCU -project 2013-2014 Final stages of disposal: temperature that of the surrounding bedrock (10 °C), all

oxygen consumed (anoxic state)

Copper in direct contact with groundwater (chemistry stabilized with bentonite)

Simulated groundwater, abiotic control

Sulfate Reducing Bacteria (SRB) present

BASUCA -project started 2015 - Same environment as in MICCU-project

SRB and methanogens (MA) present

MICOR- project started 2015 – Early stages of disposal: higher temperature (37 °C), oxygen present (oxic state)

copper in direct contact with groundwater (Onkalo PH22) with bentonite (MX80)

ammonium oxidizers (AOB) present (+ natural microbes from PH22)

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Results from our studies

All in mg l-1 Initial (MICCU)

pH 7.78

Na 3610

Cl 5340

SO4 582

Ca 279

Mg 102

K 87.5

Br 42

HCO3 13.7

Sr 7.71

Si 6.25

B 1.38

F 0.74

Mn 0.168

C3H5NaO3 1

Cu

S2-

alkalinity mmol/l 0.184

Fe2+ mg/l <0.010

sulphide mg/l 0.271

fluoride mg/l <2.00

chloride mg/l 8350

nitrate mg/l <4.00

nitrite mg/l <4.00

sulphate mg/l <6.00

phosphate mg/l <0.040

TOC mg/l 1.52

CO2, free mg/l 5.33

(HCO3-) mg/l 11.2

CO2, total mg/l 13.4

Al mg/l <0.010

Ca mg/l 1830

Cr mg/l

<0.001

0

Cu mg/l

<0.001

0

Fe mg/l 0.0081

Mg mg/l 28.4

Mn mg/l 0.106

Ni mg/l 0.0022

Ag mg/l

<0.001

0

Na mg/l 2800

Zn mg/l

<0.002

0

Si µg/l 3270

S µg/l 4740

pH 6.91

Total N mg/l 0.87

ammonium mg/l 0.135

Initial, MICOR

111119/12/2016

Experimental:MICCU&BASUCA

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Experimental: MICOR

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Measurements

Electrochemical measurements: Open circuit potential (OCP)

Linear polarization resistance (LPR) for general corrosion rate

Tafel plots to obtain the Beta coefficient values

Electrochemical impedance spectroscopy (EIS) to sudy surface processes

Electrical resistance (ER) probe, which measures real-time the thickness reduction

due to corrosion

EFM- (electrochemical frequency modulation) measurements

Gravimetric measurements:

mass loss determinations → average corrosion rate calculated

Visual and surface analyses

stereomicroscope, EDS/SEM, XRD

Microbiological studies quantitative PCR for determination of the amount of 16S rRNA gene copies in the

water and on the surface of copper

high throughput sequencing (HTP) to study the bacterial diversity, species

composition and their relative abundance in the biofilm and in the water

SEM

MICCU: SRB

BASUCA: SRB + methanogens

SRB

SRB+MAAOB

Corrosion rate, µm/ a

gravimetric LPR, max ER, max

Biotic (SRB)

4 months 6.5 13.2 45.6

10 months 1.1 3.3 14.8

Abiotic (sterile)

4 months 2.1 2.3 13.2

10 months 2.2 3.9 9.6

Biotic (SRB + MA)

4 months 0.2

12 months 1.2

Abiotic (sterile)

4 months 1.1

12 months 0.95

Biotic (AOB)

3 months 16.8-17.4

Abiotic

3 months 13.8

SRB, 4 months

mostly

alphaproteobacteria in

biofilm

SRB, 10 months,

mostly deltaproteobacteria

and clostridia

SRB+MA, 4 months

EDS: Cu, C, O, S

XRD: Cu, Cu2S, Cu2O, CuO

Abiotic, 4 months

EDS: Cu, O, C XRD: Cu, Cu2O, CuO

A&B:SRB+MA, 12

months,

EDS: Cu, C, O, S

XRD: only Cu

C&D: Abiotic

EDS: Cu, O, C

and locally Cl

XRD: Cu, Cu2O

AOB+ natural groundwater+bentonite

mainly Cu2O and CaCO3

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Preliminary conclusions

Our experimental setup seems to work well

In biotic environments the microbes had attached to the copper surface and formed

biofilm

In biotic anoxic environments the average corrosion rate (measured with weight loss) is

either clearly higher (6.5 µm/a) or at the same level (1-2 µm/a) than in abiotic

environment depending on the properties of formed surface films (Cu2S and biofilms)

It seems that enrichment of SRB might be more aggressive towards copper than

enrichment of SRB and methanogens together

Microbes in Olkiluoto groundwater are able to produce several components inducing a

risk for stress corrosion cracking (SCC)

In oxic environment the corrosion rates were higher (14-18 µm/a) than in anoxic and they

were at the same level regardless of the environment (biotic/abiotic)

According to the EIS measurements also the surface properties resembled each other

At least during short exposure time (3 months) the presence of oxygen was more

decisive for corrosion than the activity of microbes

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Conlusions cont.

These results show that the prediction of microbiological activity

and its effects to corrosion is challenging.

Thus more research, especially long exposure studies are

needed to be able to evaluate the possible influence of MIC to the

long-term safety of nuclear waste disposal concept

Articles

E. Huttunen-Saarivirta, P. Rajala, M. Bomberg, L. Carpén. 2016. Corrosion of copper in oxygen-deficient

groundwater with and without deep bedrock micro-organisms: characterisation of microbial communities and

surface processes. Submitted to Applied Surface Science.

E. Huttunen-Saarivirta, P. Rajala, L. Carpén. Corrosion behaviour of copper under biotic and abiotic

conditions in anoxic ground water: electrochemical study. Electrochimica Acta, 203:350-365.

L.Carpén, P. Rajala, M. Bomberg. 2015. Microbially Induced Corrosion in Deep Bedrock. Advanced

Materials Research Vol. 1130 (2015) pp 75-78.

P.Kinnunen, M. Bomberg, P. Rajala, L. Carpén. Industrial Views to Microbe-Metal Interactions in Sub-Arctic

Conditions. 2015. Advanced Materials Research Vol. 1130 (2015) pp 114-117.

Kutvonen, P. Rajala, L. Carpén, M. Bomberg. 2015. Nitrate and ammonia as nitrogen sources for deep

subsurface microorganisms. Frontiers in Microbiology, Vol. 6, 1079.

• E. Huttunen-Saarivirta, P. Rajala, M. Bomberg, L. Carpén, EIS study on aerobic corrosion of copper in

ground water: influence of micro-organisms. Submitted to Electrochimica Acta

Conferences and workreports:

L.Carpén, P. Rajala, M. Bomberg, M. Raunio, E. Huttunen-Saarivirta. BASUCA- Vuosiraportti 2015. VTT-R-

00867-16

L.Carpén, P. Rajala, M. Bomberg. 2016. Microbially induced corrosion of copper in simulated anoxic

groundwater. Abstract and presentation at Eurocorr 2016, 11 - 15 September 2016, Montpellier, France.

L.Carpén, P. Rajala, M. Bomberg. 2015. Microbially Induced Corrosion in Deep Bedrock. Presentation in

IBS 2015 (International Biohydrometallurgy Symposium), Sanur, Bali 5-9.10.2015.

E. Huttunen-Saarivirta, P.Rajala, L. Carpén. Corrosion behaviour of copper under biotic and abiotic

conditions in anoxic ground water: electrochemical study EMCR 2015 Tróia, 24-29 May 2015.

P. Rajala, L. Carpén, E. Huttunen-Saarivirta, I. Tsitko, M. Bomberg. Vuosiraportti 2015. VTT-R-00882-16.

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