- Possible effect of catalase and porphyrin compounds - but…

(1)

!

! " #

(2)

Aerobic corrosion

- Different enzyme-driven mechanisms and models

- Possible effect of catalase and porphyrin compounds - but…

Anaerobic corrosion

- Suphate reducing bacteria, FeS and hydrogenases - New insights on the possible role of hydrogenases - but…

Perspectives ?

(3)

" # $

Microorganisms different consortia Exopolysaccharides

Proteins (enzymes)

Accumulation of compounds released from the surface and from the environment

Being attached rather suspended makes a world of difference

(CBE, Montana)

(4)

What is a biofilm ?

Pure culture of G.sulfurreducens on carbon surface

on Ir/Ta oxides

Epifluorescent microscopy

LGC, IFR40 Toulouse

ExoPolymeric Substance Bacteria with high

fluorescence

LGC, IFR40 Toulouse

(5)

$

(6)

e

^-

%

Potential (/ref)

Current

Evolution of the cathodic branch:

ennoblement of free potential

O

₂

H

₂

O

₂

, H

₂

O

& ## "#'

(7)

&

• 1957 Microbial factors of steel corrosion in seawater (Nikita N.S., Ulanovskii I.B.)

> Biofilm has an influence on marine corrosion

• 1976 Corrélation entre la forme de la pellicule primaire et la modification de la cathodique sur des aciers inoxydables en eau de mer… (Mollica A., Trevis A.)

> Seawater biofilms modify the cathodic reaction,

without modification of the anodic branch

(8)

&

!!

"!!

!

"!!

!!

#!!

$!!

! "! ! #! $! %! &! '!

( ) *

+,)-./0*

!

" #

$ !

%

Potentiel ennoblement in Brest, Cherbourg, Genoa, Kristineberg, Trondheim

MAS programme, CNR-ICMM coordinator, from CEA-Saclay

(9)

( )#

'

! ). / / 0 ( ! ( 11 '2 13

! " #$

%

& $ $ $

'

$ #4 . 5 ( ( ( 6 1 %2 6

(

2 &

)

7 8 9: ; ( ! ( 1% ' 32'6

(10)

# " * ! '

&

^'

Laccase - active site = 4 Cu

- catalyses oxygen reduction with aromatic amines or phenol as electron donor

Catalase - Peroxidase - Superoxide dismutase ?

&

⁽

(11)

#

H

₂

O

₂

+ H

₂

O

₂

O

₂

+ 2 H

₂

O

4 equal subunits each 57000 Da

One molecule of catalase can convert 5 million molecules of hydrogen

peroxide to water and oxygen each minute

Active site

porphyrin ring

(12)

# " * ! ' $

No preliminary treatment

=> hydrophobic groups on the surface (only partial coverage with water)

hydrophobic residues

) *

12/

With preliminary treatment

=> hydrophilic surface (fully wetted)

=> carboxyl groups which react with amines of the polypeptide chain

hydrophobic residues

Glassy carbon electrode

CNRS-LGC, M.E.Lai, JEAC 2000

(13)

# " * ! ' $

NaCl 24.5 g/l

URB66 = Cr 23.92 – Ni 21.90 – Mo 5.44 – Mn 2.99 – Cu 1.54 – W 1.86 - N 0.47

Voltammetry 10mV/s

Clean SS

Porphyrin adsorbed on SS

Iron porphyrin adsorbed on stainless steel URB66

!3!"

!3!!4

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" !35 !34 !3' !3& !3% !3$ !3# !3 !3" !

6 )-. 0/)

7 8 ) *

+ 8

8

EFC 45 chap.5 R.Basséguy et al.

(14)

+ ( # # # # #

(15)

∆ ! "

# $

∆ %

∆

∆ ∆

+

(16)

-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4

-500 0

500

-800 -600 -400 -200 0 200 400 600 800

-2 -1 0

X (µµµµm) Y (µµµm)µ

Iz (µµµµA/cm²)

-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4

-500 0 500

0 -500 500

-1.8 -1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2

X (µµµm)µ Y (µµµµm)

Iz (µµµµA/cm²)

SVET on glassy carbon electrode

Porphyrin 1 central plot -0.32 V/SCE

CNRS-LGC, H.Iken, unpublished

, #

(17)

-0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1

-1000

0

1000 -1000 -500 0 500 1000

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4

Y (µµµm)µ X (µµµµm)

Iz (µµµµA/cm²)

, #

Porphyrin surrounding a clean central plot

-0.32 V/SCE

SVET on glassy carbon electrode

(18)

-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

-1000 -500

0 500

1000 -1000 -500

0

500

1000 -0.4

-0.2 0 0.2 0.4 0.6

Y (µµµµm) X (µµµm)µ

Iz (µµµµA/cm²)

-5 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0

-1000 -500 0 500 1000

-1000 0

1000-6 -5 -4 -3 -2 -1 0 1

X (µµµµm) Y (µµµµm)

Iz (µµµµA/cm²)

SVET on stainless steel URB66

Porphyrin 1 central plot

-0.50 V/SCE

without hemin, scale X 7

, # # #

(19)

& ( ' # $

Powerful models able to reproduce biocorrosion in the lab (MOB, GOD, hopefully porphyrin…)

Each model corresponds to particular natural conditions (high concentration of Mn ions, high concentration of substrate…)

Each has a part of the “code”

Even more inter-penetration of the thematic areas is still required…

And more…

(20)

-800 -600 -400 -200 0 200

-500 -300 -100 100 300

Potential (mV vs. SCE)

Current (µA)

&" # !

" #

# " # # #

A.Bergel, D.Féron, A.Mollica, Electrochem.Comm. 2005

Stainless steel URB66

Current density

up to 1.3 A/m

²

(21)

e

^-

H

⁺

Sulphate Reducing Bacteria

Fe

²⁺

S

^2-

(H

₂

S)

Precipitation of iron sulphide

SO

₄^2-

½ H

₂

electron donors

H

⁺

½ H

₂

Iron sulphide catalyses proton reduction, depending on its composition, crystal

structure, surface defects, age…

(adsorption of atomic hydrogen may decrease the catalytic effect…)

& (

(22)

# " ! $ - " $.

H

₂

<==> 2 H

⁺

+ 2 e-

& (

• It has been claimed that the presence of HYDROGENASE may have a key role

• It has also been claimed that the presence or not of hydrogenase has no effect

• … but kits are commercialized to measure hydrogenase activity in order to assess

corrosion risks

(23)

e

^-

H

⁺

Fe

²⁺

S

^2-

Precipitation of iron sulphide

½ H

₂

H

⁺

½ H

₂

Consumption of H

₂

shifts the

equilibrium towards proton reduction

H

₂

evolution is a non-reversible process on carbon steel

H

₂

removal cannot be rate-limiting

, ! ( / ! /

(24)

Rajagopal and Le Grall (1989) Belay and Daniels (1990)

BSR

mild steel Bryant et Laishley (1990)

Hydro- genase

Mild steel

Corrosion increase

Intervention of FeS

Consumption of H₂

Corrosion increase

Confirmation of consumption of H₂

0' / *)

Displacement of the equilibrium of

reduction de H

⁺

or H

₂

O?

(25)

)

&

+ ,

-

) . /

01!234

12 3 #'

- +

,.)

5 6

2 4 ) #

L.DeSilva-Munoz, A.Bergel, R.Basseguy Corrosion Science 2007

(26)

K-phosphate 10, 50, 150, 500 mM, pH 8.0 - RDE 2mm SS316L electrode

# ) " ) )

0.1M KCl, rotating speed 1000 rds/min, potential scan rate 20 mV s^-1.

Preliminary 5-minute electrolysis at -0.50V/SCE before each scan.

(27)

) " ) ) )

2e

^-

2 H

₂

PO

₄^-

'

* +

(

2 HPO

₄^2-

, *

₎

Fe Fe

²⁺

+ # - % $ . /0

' 1 /0 /2

# ) " ) )

(28)

Looking for reversibility ?

SS 316L

# ) " ) )

0.1M KCl

0.1M KCl + 1 mM H

₂

PO

₄

-0,70 -0,60 -0,50 -0,40 -0,30

0,0 1,0 2,0 3,0 4,0

Time (h)

E (V/SCE)

N₂ H₂-25% H₂50% H₂-75%

(29)

CNRS-LGC, S.DaSilva JEAC 04, EA 04

Electrochemical deprotonation of phosphate species

NAD⁺

2e

^-

2 H

₂

PO

₄^-

What could be the cathodic reactions that enhance corrosion rate?

Direct electron transfer

demonstrated on stainless steel

Recently direct oxidation of metallic powders with H₂ production

(Zadvorny et al. 2006)

2 HPO

₄^2-

+ H

₂

NADH

H

⁺

NAD⁺

2e

^-

NADH

H

⁺

# ) ) !

, ! "

(30)

5 "- . 4 ) 6 7 ), 8 / / ' ,

/ - 9: ;. , / ' ,

7 .) 8

& , ! ) )

CNRS-LGC, M.Mehanna, unpublished

3456

(31)

/ ' ) )

5 "- . , # < 7 ), =8 / / ' ,

7 9) 8

/ -=>: ;. , / ' ,

CNRS-LGC, M.Mehanna, unpublished

(32)

4 # # "

,

( '

-

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(

,

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1 8;

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=

1 8

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(33)

? Revisiting the previous lab studies taking into account

possible involvement of phosphate species (common buffer)

? Towards the end of the domination of the FeS hypothesis?

YES - SRB corrosive activity has been detected before significant sulfide

production (D.capillatus, from oil field separator Mexico, Miranda et al. Corr.

Sci. 2005)

- Direct electron transfer from iron to Desulfobacterium-like (Dinh et al.

Nature 04)

- Direct electron transfer of different free hydrogenases

- Electro-Deprotonation of weak acids present in biofilm (LGC-CNRS De Silva under preparation)

NO - Switching SRB from sulfate metabolism to nitrate metabolism stopped corrosion

(34)

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