Towards a unified approach on a European scale of electrochemical hydrogen permeation test methodologies on low alloyed steels

Directorate-General For Research And Innovation European Commission

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Industrial research and development

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• Sciences et techniques

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• Publié par: DIRECTORATE-GENERAL-FOR-RESEARCH-AND-INNOVATION-EUROPEAN-COMMISSION
• Nombre de lectures: 60
• Langue: English
• Poids de l'ouvrage: 6 Mo

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ISSN 1018-5593
European Commission
technical steel research
Properties and service performance
Towards a unified approach on a European
scale of electrochemical hydrogen
permeation test methodologies
on low alloyed steels
STEEL RESEARCH European Commission
technical steel research
Properties and service performance
Towards a unified approach on a European
scale of electrochemical hydrogen
permeation test methodologies
on low alloyed steels
L. Scoppio,1 J. Brogan,2 L. Coudreuse,3 A. Brass,4 M. LamberigsV
J. Servais,5 Ó. Jessen,6 J. Durand,7 E. Riecke6
CSM
2 British Steel
aCLI
4CNRS
5CRM
•FI
'IRSID
•MPI
Contract No 7210-KB/430
1 December 1990 to 31 December 1993
Final report
Directorate-General
Science, Research and Development
1997 EUR 16790 EN LEGAL NOTICE
Neither the European Commission nor any person acting on behalf of the Commission
is responsible for the use which might be made of the following information
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It can be accessed through the Europa server (http://europa.eu.int)
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1997
ISBN 92-828-1123-9
© European Communities, 1997
Reproduction is authorized provided the source is acknowledged
Printed in Luxembourg TABLE OF CONTENTS
SUMMARY
21
1. OBJECTIVES OF THE RESEARCH
21
1.1 - General Objectives
1.2 - Specifics 22
2. INTRODUCTION3
21. - Diffusion
2.2 - Boundary conditions
2.3 - Characteristic diffusion features 24
2.4 - Trapping. Short paths for diffusion. Surface phenomena5
2.5 - Principle of the electrochemical permeation test6
2.6 - Theoretical diffusion curve7
2.7 - Diffusion coefficient and permeation flux8
3. EXPERIMENTAL 29
3.1-Materials 32
3.1.1 - Preparation of the 1st pure iron bar
3.1.2- Preparation of 2nd pure iron bar
3.1.3- X65 steel material3
3.1.4 - HIC susceptibility4
3.1.5 - Other materials
3.2.1 - Specimen preparation and geometry ^5
3.2.2 - Test conditions 33.2.3 - Procedure of the round robin test 35
3.3 - Modification of the test procedureg
4. RESULTS 37
4.1 - Preliminary investigation
4.1.1 - Potentiodinamic curves in 0. IN NaOH
4.1.2- Evolution of anodic current density under effect of step wise bias variation 37
4.2 - Hydrogen permeation through passivated iron 3g
4.3 - Effects of the iron membrane thickness9
4.4 - Round robin test results 40
4.4.1 - Cathodic potential on the entry face during permeation test 41
4.4.2 - Diffusion coefficient2
4.4.3 - Assumption on the boundary conditions on the entry side4
4.5 - Modified test results 45
4.5.1 - Modification of the round robin test procedure: potentiostatic charging 4
4.5.2 - Influence of oxygen in the charging solution6
4.5.3 - Influence of modification of the charging current density 4
4.5.4 - Effect of 3rd and 4th galvanostatic charging on hydrogen permeation7
4.5.5 - Effect of X65 sample thickness9
4.5.6 - Effect of temperature variation on X65 steel specimens 51
4.5.7 - Effect of palladium coating on hydrogen permeation
4.5.8 - Effect of palladium coating on the hydrogen diffusivity of MPI experiments 5
4.5.9 - Effect of palladium coating on BST experiments 53
4.5.10- Effect of palladium coating on CNRS experiments4
4.5.11 - Effect of palladium coating on CRMs6 4.6 - Theoretical Modelling and CRM Optimized Data Processing 56
4.6.1 - Hydrogen diffusion coefficient assestment 5
4.6.2 - Trapping mechanism8
5. DISCUSSION 62
6. CONCLUSIONS6
6.1 - Test results (Round Robin Test)
6.2 - Test results (specific research activities)7
7. REFERENCES9
TABLES 71
FIGURES 92
AMEJL1 153
Pd coating methods
ANNEX Π7
Hydrogen permeation and degassing data on pure iron X 65 steel
ANNEX ΙΠ 17
Experiments on sealed Devanathan Cell couples
ANNEX IV 191
Hydrogen permeation and degassing data on X 65 steel of different thickness
ANNEX V7
Gas phase charging experiments
ANNEX VI 20
Hydrogen permeation and degassing data on pure iron and X 65 steel following an
improved data processing procedure SUMMARY
Electrochemical permeation test is widely used due to its versatility and high sensitivity.
However, the comparison of data obtained by different laboratories is often difficult due to
the number of parameters to be controlled.
This work, involving eight european research laboratories is aimed to improve the
knowledge of the different experimental parameters to be taken into account in order to
conduct reliable permeation tests in the near room temperature range.
The same experimental procedure (round robin) was applied by all participating laboratories
to reference pure iron, and commercial linepipe X65 carbon steel specimens. Several series
of hydrogen permeation tests were performed. The agreeded procedure required some
recommendation to be followed:
The charging solution must be carefully deaerated since oxygen induces delayed hydrogen
permeation and distorsions in the permeation curves.
The mechanical surface preparation of low strength materials must be carried out most
carefully to avoid an increase in trap densities. This effect is less important for commercial
steels.
Scatter of the permeation results was observed probably due to surface phenomena related
to hydrogen interactions with microstructural defects on the entry and exit face of the
samples (carbides, inclusions, dislocations, interfaces, ...).
A strong effect of Pd coating has been observed.
Pd coating on the entry side is not beneficial. Pd coating on the exit side leads to an
increase in the maximum permeation current if the surface is sputtered with argon ions
before palladium deposit.
Pd deposited on both faces of the samples leads to a 5 to 6-fold increase in the permeation
flux.
Test results showed a clear relationship between the maximum permeation current and the
value of the cathodic potential on the entry face of the samples was observed. The more
negative the potential on the entry face, measured when the maximum permeation current is
reached, the larger the permeability.
Round Robin test carried out on X65 steel gave the following diffusivities coefficient
values. From data obtained from 1st charging:
Dtb(tg) = 4.50-8.80 · IO"7 cm2 s"1
Dü(0.617 ia(max)) = 1.03 -9.26 -IO"? cmV* From data obtained from 2nd charging:
Dtb(tg) = 5.12-10.80 · IO"6 cm2 s"1
Hydrogen diffusivities depending on shallow and deep traps can be obtained only from first
charging tests using the initial part of the permeation transients.
Hydrogen diffusivities depending only on both shallow traps can be obtained from second
charging tests using various analytical methods, or from degassing tests if the deep traps are
occupied as far as possible. TABLE AND FIGURE CAPTIONS
Tab. I - Expressions for D calculation
Tab. II - Chemical composition of pure iron and X65 steel
Tab. 111(a) - Specimen preparation, geometry and cell configuration adopted by the
different laboratories
Tab. 111(b) - Test conditions adopted by the different laboratories
Tab. IV - Determination of the inclusions content in X65 steel (CSM)
Tab. V - Comparison among hydrogen diffusion coefficients estimates of pure iron 1st
ingot. In brackets is reported the number of test performed
Tab. VI - Comparison among hydrogen diffusion coefficients estimates of X65 steel.In
brackets is reported the number of test performed
Tab. VII - Permeation data of hydrogen in pure iron obtained with galvanostatic (2 and
4 mA/cm2 ) and potentiostatic (E = -1105 mVH.) charging (NaOH 0.1N,
25 °C)
*( ) degassing ( ) number of tests (CNRS)
Tab. VIII - Hydrogen permeation and degassing data of X65 line pipe steel (H62).
Potentiostatic charging at -1105 mVH (CNRS)
Tab. IX - Hydrogen permeation and degassing data of X65 line pipe steel: galvanostatic
charging at 2 mA/cm2 (CNRS)
Tab. Xa - Results from the second series of JP permeation experiments with the 1st
pure iron; first and second charging and degassing. A subsequent third and
fourth charging and a second degassing were performed. These results are
given in TabXb (FI)
Tab. Xb - Results from the second series of JP permeation experiments of the 1st pure
iron. The table shows the results of the third and fourth charging and second
degassing of the experiments DV-211 and DV-212 in the table above. Please
note that the DV-211 was only allowed to degas (1st ) for 2 hours while the
DV-212 was degassing for 22 hours. In addition, the duration of the 3rd and
4th chargings were different for the 2 experiments (FI)