Delpoux, Olivier

Desamais, N.

Grosjean, François

Joiret, Suzanne

Kittel, J.

Taravel-Condat, Carol

English

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A study by in situ Raman spectroscopy of carbon steel
corrosion in CO2 and H2S environment
Olivier Delpoux, J. Kittel, François Grosjean, Suzanne Joiret, N. Desamais,
Carol Taravel-Condat
To cite this version:
Olivier Delpoux, J. Kittel, François Grosjean, Suzanne Joiret, N. Desamais, et al.. A study by in
situ Raman spectroscopy of carbon steel corrosion in CO2 and H2S environment. Eurocorr 2013, Sep
2013, Estoril, Portugal. ￿hal-02464641￿
200 400 600 800 1000 1200
7jdays
5 days
12 days
14 days
18 days
280 cm
-1
 
nanomackinawite
and/or FeCO
3
292 cm
-1
 
Mackinawite
670 cm
-1
 
Magnétite
In
te
n
si
ty
 (
a.
u
.)
Raman shift (cm-1)
1082 cm
-1
 FeCO3
26 days
0  5 days : no iron salts detected 
200 400 600 800 1000 1200
t=9 days
t=7 days
t=6 days
t=5 days
282 cm
-1
 (O-Fe-O) 
In
te
n
si
ty
 (
a.
u
.)
Raman shift (cm-1)
980 cm
-1
(K
2
SO
4
)
1082 cm
-1
 (C=O)
in FeCO
3
 
t=0 days
Raman analyses were carried out on a Horiba LabRam Aramis using a frequency-doubled Nd:YAG laser (lexc=532 nm), an 
Olympus confocal microscope equipped with a 50X LWD (Long Working Distance) objective (-> the diameter of the studied 
zone is  around 2 µm).  
Then the Raman signal is collected by a back-scattering configuration and dispersed with a 1200/mm grating and collected by 
a CCD detector. The spectral resolution obtained is around 1.5 cm-1. 
Finally, the analytical conditions depend on the species : 
 Carbonates species only :  Sulfides species : 
- moderate acquisition time  - long acquisition time 
- moderate to high laser power - low laser power 
A study by in situ Raman spectroscopy of carbon steel 
corrosion in CO2 and H2S environment 
O. Delpoux,a J. Kittela, F. Grosjeana, S. Joiretb, N. Desamaisc, C. Taravel-Condatc  
a  IFP Energies Nouvelles, Rond-point de l'échangeur de Solaize BP 3, 69360 Solaize, France 
b  CNRS, UPR15, Laboratoire Interfaces et Systèmes Electrochimiques, F-75005 Paris, France  
c   Technip, rue Jean Huré, 76580 Le Trait, France  
Background and Objectives 
Corrosion products formed in oil and gas exploration & production environments are very often composed of iron carbonate and / or iron sulfide. The impact of such deposits on corrosion largely 
depends on their composition, thus on the ratio between partial pressures of both gases. A classical rule-of-thumb considers a dividing line between sweet and sour corrosion where the ratio of CO2 
and H2S partial pressure is 500. However, a recent review of thermodynamic calculations showed that the error band for the calculation of this ratio threshold was extremely large [1]. It is also well 
known that the composition of corrosion products observed in field exposures evolves over long periods of time, especially for iron sulfides that can change from mackinawite to pyrrhotite [2], the latter 
forming preferentially at higher temperature and high PH2S. Besides, most of sulfides species are very sensitive to oxydation after removal from the exposure environment. It is therefore useful to 
develop in situ methods. 
Raman spectroscopy is a vibrationnal spectroscopy commonly used to describe iron sulfides with high resolution [3,4] and can carry out in situ analyses using immersion probe or a specific cell 
equipped with a window. 
    The aim of this work is to explore the potentialities of this technique to characterize in situ corrosion products formed in CO2 and H2S environments 
Experimental 
 2days : no iron salts detected 
5 days : mackinawite (292 cm-1) and 
magnetite (670 cm-1) appeared 
[1] S.N. Smith, Discussion of the history and relevance of the CO2/H2S ratio, Corrosion/2011 paper no065, NACE International (2011) 811-818  
[2] S.N. Smith, B. Brown, W. Sun, Corrosion at higher H2S concentrations and moderate temperatures, Corrosion/2011 paper no081, NACE International 
(2011) 
Conclusions 
Raman spectrometry  permits in situ monitoring of the corrosion process under both H2S and CO2 environments in a qualitative way. 
For a 1000 ppm H2S/CO2 atmosphere, only iron sulfides are detected  
For a 100 ppm H2S/CO2 atmosphere, this methodology shows that iron sulfides appear first followed by iron carbonates 
 
The study of the heterogeneity puts in evidence the issue of the significativity of the measure. The analyzed area must be increased by using new mapping 
technologies such as Duoscan (Horiba) or Streamline (Renishaw) 
Results 
[3] J.A. Bourdoiseau, M. Jeannin, C. Rémazeilles, R. Sabot, and P. Refait, Journal of Raman Spectroscopy, 2011, 42, 496-504  
[4] MC. Bernard, S. Duval, S. Joiret, M. Keddam, F. Ropital, and H. Takenouti, Progress in Organic Coatings, 2002, 45, 399-404  
Methodology Apparatus 
 
Design of the cell taking into account the Raman constraints : 
- Dimensions : the cell must be put on the motorized mapping stage 
- Focusing : distance sample <-> LWD objective ≤ 10 mm 
- Signal quality : glass window must be as thin as possible 
 
Validation of the analysis cell on a simple case : 
- Study of a steel specimen under pure CO2 pressure  
- Study of a steel specimen under pure H2S pressure  
The cell and methodology is validated : this development permits to analyze  
in situ both sulfides and iron carbonates in a qualitative way 
Under these conditions and 
with CO2 / H2S = 10
3 
sulfides appear first and 
carbonates are not observed 
> 5 days : only a band at 282 cm-1 is detected   
 FeS in a Mackinawite structure 
 
2  9 days : bands at 282 and 1082 cm-1  FeCO3 
Validation in pure CO2 at 80° C 
Study of the competition between sulfides and carbonates at 100 and 1000 ppm H2S/CO2 
7 days : iron carbonates are suspected  
perilstatic pump 
cell 
thermostated cell for 
gas bubbling 
Corrosion experiment conditions 
- Low alloy steel specimens 
- Exposure in pure water saturated with CO2 + H2S 
- Strict de-aeration conditions 
150 200 250 300 350 400 450 500
1 day
8 days
380 cm
-1
340 cm
-1
280 cm
-1 296 cm
-1
206 cm
-1
In
te
n
si
ty
 (
a.
u
.)
Raman shift (cm-1)
480 cm
-1
7 days
Validation in pure H2S at ambient T° 
1 7 days : well crystallized mackinawite (296 cm-1) + pyrite (340 and 380 cm-1) 
No signal of S8  
at 480 cm-1 : 
laser power  
is not too high 
8 days : formation of nano-mackinawite (280 cm-1) in addition to the previous species 
Ex situ study of the heterogeneity  
(specimen with iron sulfides + iron carbonates) 
200 400 600 800 1000 1200
day 4
day 1
day 2
day 3
day 5
280 cm
-1
 
nanomackinawite
and/or
 FeCo3
296 cm
-1
 
Mackinawite
In
te
n
si
ty
 (
a.
u
.)
Raman shift (cm-1)
1082 cm
-1
 FeCO3
- 1 measure every day  
during 5 days 
- cell is kept under  
vacuum between 2 spectra 
Ratio of carbonates to sulfides depends on the spot : 
 surface coverage by corrosion scale is heterogenous 
 Analysis should be averaged with several spots 
12 days : iron carbonates are detected  
>12 days : magnetite has disappeared 
Ambient T° - 1000 ppm H2S/CO2 
Under these conditions and 
with CO2 / H2S = 10
4 
sulfides appear first and then 
both carbonate and sulfides 
are observed simultaneously 
Ambient T° - 100 ppm H2S/CO2 
200 400 600 800 1000 1200
6 days
5 days
4 days
282 cm
-1
 
nanomackinawite
and/or FeCO3
11 days
7 days
5 days
12 days
292 cm
-1
 
Mackinawite
In
te
n
si
ty
 (
u
.a
.)
Raman shift (cm-1)
1082 cm
-1
 FeCO3
1 
1 
1 


A study by in situ Raman spectroscopy of carbon steel corrosion in CO2 and H2S environment

https://hal-ifp.archives-ouvertes.fr/hal-02464641/document

A study by in situ Raman spectroscopy of carbon steel corrosion in CO2 and H2S environment

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