Modeling of Beryllium Corrosion Anrc9930 1999

7/28/2019 Modeling of Beryllium Corrosion Anrc9930 1999

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ANRCP-1999-30October 1999

Amarillo National

Resource Center for PlutoniumA Higher Education Consortium of The Texas A&M University System,Texas Tech University, and The University of Texas System

Modeling of Beryllium Corrosion

Juan Sanchez, Sheldon Landsberger, and Li ZhaoMechanical Engineering Department

The University of Texas at Austin

Edited by

Angela L. WoodsTechnical Editor

600 South Tyler Suite 800 Amarillo, TX 79101(806) 376-5533 Fax: (806) 376-5561

http://www.pu.org

This report was

prepared with the

support of the U.S.

Department of Energy

(DOE) Cooperative

Agreement No. DE-

FC04-95AL85832.However, any opinions,

findings, conclusions,

or recommendations

expressed herein are

those of the author(s)

and do not necessarily

reflect the views of

DOE. This work was

conducted through the

Amarillo National

Resource Center for

Plutonium.


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ANRCP-1999-30

AMARILLO NATIONAL RESOURCE CENTER FOR PLUTONIUM/A HIGHER EDUCATION CONSORTIUM

A Report on


Juan Sanchez, Sheldon Landsberger, and Li ZhaoDepartment of Mechanical Engineering


Austin, Texas 77812

Submitted for publication to

ANRC Nuclear Program

October 1999


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Juan Sanchez, Sheldon Landsberger, and Li Zhao

Department of Mechanical Engineering


Abstract

This research examined whether

experiments concerning beryllium corrosioncan be conducted at room temperature with no

adverse affects. Because corrosion depends

on the respiratory environment, mechanismsand parameters associated with corrosion

must be identified. There are 3 stages in the

evolution of storage conditions. The ability toidentify beryllium corrosion at various stages

would be ideal.

Actual temperature for beryllium

metal cladding is approximately 50C. In

calculating the Pourbaix diagram of beryllium

at room temperature (50C) by Nerstequations, the diagram indicated a passivity

range between pH 4 and pH 11. Comparing

the passivity region at room temperature,

almost no change at 50C could be seen; in

effect, room temperature did not affect thepassivity of beryllium in aqueous solutions.


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iii

TABLE OF CONTENTS

1. INTRODUCTION................................................................................................................... 1

2. IDENTIFICATION OF BERYLLIUM CORROSION....................................................... 2

3. THERMODYNAMIC CALCULATIONS FOR BERYLLIUM WITHIN

CHLORINATE SOLVENTS................................................................................................ 5

4. POURBAIX DIAGRAM OF BERYLLIUM AT 50C ...................................................... 11

5. CONCLUSIONS ................................................................................................................... 13

REFERENCES........................................................................................................................... 15


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iv

LIST OF FIGURES

Figure 1: Property Diagram of BeO in TCA ............................................................................... 6

Figure 2: Property Diagram of BeO in TCE................................................................................ 6

Figure 3: BeCl2 in Solvents with Different Ratios of H/Cl.......................................................... 8

Figure 4: BeCl2 in Solvents with H/CL of Zero........................................................................... 8

Figure 5: The Property Diagram of BeO in CCl4......................................................................... 9

Figure 6: Pourbaix Diagram of Beryllium at Room Tempera*ture ........................................... 12

Figure 7: Pourbaix Diagram of Beryllium at 50C.................................................................... 12


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LIST OF TABLES

Table 1: Product of BeCl2 in Different Solvents......................................................................... 7


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1

1. INTRODUCTION

In 1998, the research on a study of thecorrosion of beryllium was performed in

three areas: (1) mechanisms and parameters

associated with corrosion have been

identified by a literature review; (2) the

effects of the chlorinated solvents used in the

cleaning process on beryllium corrosion havebeen considered by thermodynamic

calculations; and, (3) the effect of

temperature on the passivity of beryllium

was described by Pourbaix diagrams.


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2. IDENTIFICATION OF BERYLLIUM

CORROSIONThere are many published papers

available about the corrosion of stainless

steel, but just a few about beryllium

corrosion. Because corrosion depends onthe repository environment, such as

temperature, and aggressive anions such asCl-, mechanisms and parameters associated

with corrosion must be identified.

There are three stages in theevolution of storage conditions, called Phase

0, Phase 1, and Phase 2. The first stage,

called Phase 0, is during the storage-

operating period. During this period, dry

general corrosion and pitting corrosion may

occur at ambient temperature because of theexistence of sufficient oxygen and aggressive

anions such as Cl-. The second stage, called

Phase 1, occurs immediately after the

containers have been sealed. In this stage,either dry or aqueous general corrosion may

occur depending on the humidity in thecontainer. Also oxygen is still available to

cause pitting corrosion although oxygen is also

consumed by the general corrosion. The thirdstage, called Phase 2, occurs after oxygen has

been consumed. In this period, general

corrosion becomes dominant and slow, and

pitting corrosion does not happen.


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3. THERMODYNAMIC

CALCULATIONS FOR

BERYLLIUM WITHIN

CHLORINATE SOLVENTS

When beryllium is exposed in air at

room temperature, a film of beryllium oxideforms quickly on the surface. Because

beryllium alloys contain about 0.2%impurities of carbon, these carbon atoms can

react with the water from air to form

beryllium oxide as follows:

422 22 CHBeOOHCBe ++

Chloride ions are suspected to cause

the beryllium pitting corrosion. These

chloride ions can potentially come fromthree sources. First, beryllium metalcontains chlorides; second, the Celotex

packaging material contains chlorine and

thus may be liberated as a chloride under theright environmental conditions; and third,

chloride arises from the chlorinated solvents

1,1,1-trichloroethylene (TCA), and 1,1,2-

trichloroethane (TCE) during the process forcleaning weapons components. Given

property diagrams of beryllium oxide in

TCA, TCE, and carbon tetrachloride, onecan predict the beryllium corrosion. These

property diagrams were generated by

simulating the interaction of beryllium oxidewith TCA, TCE, and carbon tetrachloride by

the computer program Thermo-Calc.

Thermo-Calc is a powerful andflexible software for all kinds of

thermodynamic parameters and phase

diagram calculations. It is used to predict

properties of materials and processes.

A system including ,BeO ,2CO ,2O

,2OH and the solvent at room temperature and

at 1 atm pressure is used in Thermo-Calc.

Although the operating temperature is about50C in the actual cleaning processes, there are

almost no differences at a temperature of 25 or

50C when comparing the property diagrams ofBeO in TCA or TCE. Therefore, all

calculations in this study were done at room

temperature. The property diagrams of BeO inTCA and TCE are shown in Figures 1 and 2.

These figures show that beryllium

chloride is formed by exposing beryllium oxideto TCE, but not on exposing it to TCA.

Therefore, the ratio of the hydrogen to chloride(H/Cl) in the solvents may play an importantrole to form the corrosion product, beryllium

chloride. In order to reveal the influence of

H/Cl ratio on the beryllium corrosion, the

property diagrams for 20 chlorinated solventshaving the ratio of H/Cl from 0 to 5 were done

by Thermo-Calc. The results are shown in

Table 1. These results suggest that (a) carbonis essential to form beryllium chloride from

beryllium oxide, and (b) a ratio of H/Cl


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Figure 1: Property Diagram of BeO in TCA

Figure 2: Property Diagram of BeO in TCE

0

5

10

15

20

25

0 0.5 1 1.5 2 2.5

N(C2Cl3H3)/N(H2O)

NP(MolesofPh

ase)

Gas H2O(L) BeO(S)

0

5

10

15

20

25

0 0.5 1 1.5 2 2.5

N(C2Cl3H)/N(H2O)

NP(molesofPhase)

Gas H2O(L) BeO(S) BeCl2(Beta)


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Table 1: The Product of BeCl2 in Different Solvents

Name FormulaBeCl2

Product

H/Cl

inthe Solvent

C

inthe Solvent

Carbon tetrachloride CCl4 Yes 0/4 1

Chloroform CCl3H Yes 1/3 1Dichloromethane CCl2H2 No 2/2 1methyl chloride CClH3 No 3/1 1

Tetrachloroethylene C2Cl4 Yes 0/4 2

trichloroethylene C2Cl3H Yes 1/3 2dichloroethylene C2Cl2H2 No 2/2 2

vinyl chloride C2ClH3 No 3/1 2

hexachloroethane C2Cl6 Yes 0/6 2

pentachloroethane C2Cl5H Yes 1/5 2tetrachloroethane C2Cl4H2 Yes 2/4 2

trichloroethane C2Cl3H3 No 3/3 2

ethylene dichloride C2Cl2H4 No 4/2 2ethylene chloride C2ClH5 No 5/1 2

hexachlorobenznene C6Cl6 Yes 0/6 6

pentachlorobeznene C6Cl5H1 Yes 1/5 6tetrachlorobenznene C6Cl4H2 Yes 2/4 6

trichlorobenznene C6Cl3H3 No 3/3 6

dichlorobenznene C6Cl2H4 No 4/2 6

monochlorobenznene C6ClH5 No 5/1 6

Figure 3 shows that BeCl2 increasesas the ratio of solvent to water increases and

as the H/Cl ratio decreases, while Figure 4shows the same pattern even with a H/Clratio of zero.

Considering these results, it

suggested to use the solvents with less

carbon containing a higher ratio of H/Cl inthe cleaning process. However, these

predictions, based on theoretical

calculations, need to be verified

experimentally. In addition, the effect of thesolvents with a ratio 1 needs to be

experimentally assessed.In order to find the influence of Cl

-in

Celotex on beryllium metal, CCl4 is chosen to

simulate the reaction between BeO and Cl-. The

property diagram is shown in Figure 5.

From Figure 5, it can be deduced thatCl- in CCl4 causes corrosion of BeO to form the

product of BeCl2. Therefore, Cl- in Celotex can

potentially lead to beryllium corrosion.


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Figure 3: BeCl2 in Solvents with Different Ratios of H/Cl

Figure 4: BeCl2 in Solvents with H/Cl of Zero

0

1

2

3

4

5

6

7

0 0.5 1 1.5 2 2.5

N(Solvent)/N(H2O)

N(BeCl2)

CCl3H (H/Cl=0.33) C2Cl3H(H/Cl=0.33) C6Cl5H(H/Cl=0.2)

C2Cl5H(H/Cl=0.2) C2Cl4H2(H/Cl=0.5) C6Cl4H2(H/Cl=0.5)

H/Cl=0.2

H/Cl=0.33

H/Cl=0.5

0

2

4

6

8

10

12

0 0.5 1 1.5 2 2.5

N(Solvent)/N(H2O)

N(BeCl2)

CCl4 C2Cl4 C6Cl6 C2Cl6


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Figure 5: The Property Diagram of BeO in CCl4

0

5

10

15

20

25

0 0.5 1 1.5 2 2.5

N(CCl4)/N(H2O)

NP(molesofPhases)

Gas H2O(L) BeO(S) BeCl2(Beta)


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4. POURBAIX DIAGRAM OF

BERYLLIUM AT 50CMany investigations of beryllium

passivity as a function of solution pH have

been published. The Pourbaix diagram (or

potential-pH diagram) of beryllium at roomtemperature, available in the literature,

indicates a passivity region from a pH 4 to

pH 11 (Figure 6). However, the actualtemperature for the beryllium metal cladding

is around 50C. In order to understand the

passivity of beryllium to changes with thetemperature, the Pourbaix diagram of

beryllium at 50C was done by calculating

Nerst equations.

The general reaction for a half-cell

can be written:

dDcCbBaA +=+ (1)

where a is the mole of reactant A ; b is the

mole of reactant B ; c is the mole of

product C, and d is the mole of product .D

Nerst equation for the generalreaction (1) is as follows:

ba

dc

ba

dc

aa

aa

nF

RTE

aa

aa

nF

RTEE log

3.2ln

00== (2)

where E is the half-cell electrode potential;0

E is the half-cell electrode potential at

standard state; R is the gas constant; T is

absolute temperature; n is the number of

electrons exchanged in the reaction; F is

Faraday's constant, and a is the activity of

reactants or products in the reaction.

Reactions of beryllium involved in the

Pourbaix diagram are as follows:

+++= eBeBe 2 (a)

++++=+ HBeOOHBe 22 (b)

+++=+ eHBeOOHBe 222 (c)

++=+ HOBeOHBeO 22 2322 (d)

+++=+ eHOBeOHBe 4632

2

322 (e)

The Pourbaix diagram of beryllium at

room temperature was done according to Nerstequations for above reactions of beryllium in

Figure 6.The Pourbaix diagram of beryllium at

room temperature agrees with the published

literature in which a passivity region is located

from a pH 3.4 to pH 11.6. A Pourbaix diagram

of beryllium at a room temperature of 50Cwas also done (Figure 7).

Figure 7 also shows that a passivity

region is located from a pH 3.5 to pH 10.5.Comparing to the passivity region at room

temperature, there is almost no change at 50C.

Therefore, the actual temperature (50C) does

not affect the passivity of beryllium in aqueoussolutions significantly, and the data associated

with beryllium corrosion at room temperature

are applicable to an actual situation.


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Figure 6: Pourbaix Diagram of Beryllium at Room Temperature

Figure 7: Pourbaix Diagram of Beryllium at 50C

6

Immunity

0 1

- 2 . 7

- 3 . 0

- 2 . 9

- 2 . 8

- 2 . 6

- 2 . 4

- 2 . 5

42 3 5

Corros ion

Be

Pote

ntial(V)

- 2 . 0

- 2 . 3

- 2 . 1

- 2 . 2

- 1 . 7

- 1 . 8

- 1 . 9

(a)

-1 . 3

- 1 . 6

- 1 . 5

- 1 . 4

- 1 . 0

-1 . 1

- 1 . 2

++

(b)

87 109

Be

1511 12 1413

pH

(e)

(c)

B eO

Passivition

Be2-

O 32

Corros ion

(d)

Be

Immuni ty

(c)

(e)

(b)

(d)

Corrosion

Be2-

O 32

12 14138 109 11 15

pH

Corrosion

5 6 72 3 4

Passivi tion

Be O

10-3.0

++

(a )

Be

Po

tential(V)

-2.7

-2.9

-2.8

-2.6

-2.5

-2.2

-2.4

-2.3

-2.1

-2.0

-1.7

-1.8

-1.9

-1.5

-1.6

-1.2

-1.3

-1.4

-1.0

-1.1


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5. CONCLUSIONS

It is essential for the study ofberyllium corrosion to identify it during

different periods. The chlorinated solvents

can cause the beryllium corrosion because

they have the ratio of H/Cl


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REFERENCES

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photoelectron spectroscopic (XPS)

examinations of beryllium metalsurfaces exposed to chlorinated solvents.

The Journal of Surface and InterfaceAnalysis (to be published).

2. Henshall, G. A. (1996). Aphenomenological approach tosimulating the evolution of radioactive-

waste container damage due to pitting

corrosion. Materials Research SocietySymp. Proc. 412, 613-619.

3. Hill, M. A., Butt, D. P., and Lillard, R.S. (1997). The passivity and breakdownof beryllium in aqueous solutions. The

Journal of the Electrochemical Society,

145(8), 2799-2806.

4. Hill, M. A., Butt, D. P., and Lillard, R.S. (1996). The corrosion/electrochemistry of beryllium and

beryllium weldment in aqueous chloride

environment. Internal Los AlamosNational Laboratory Report to bedistributed to Pantex and Lawrence

Livermore National Laboratory

Personnel.

5. Jones, D. A. (1996). Principles andprevention of corrosion (2nd ed.). Upper

Saddel River, NJ: Prentice-Hall, Inc.

6. Korb, L. J., Olson, D. L. et al. (1987).

Metals handbook (9th

Ed.) V. 13. MetalsPark, OH: American Society for Metals.

7. Lee, J. H., Atkins, J. E., and Andrews, R.W. (1996). Humid-air and aqueouscorrosion models for corrosion-

allowance barrier material. Materials

Research Society Symp. Proc., 412, 571-

580.

8. Lillard, R. S., Hill, M. A., and Butt, D. P.(1997). Preliminary investigation into the

corrosion of beryllium exposed to Celotexand water. Internal Los Alamos National

Laboratory Report to be distributed to

Pantex and Lawrence Livermore NationalLaboratory Personnel.

9. Marsh, G. P., Bland, I. D., and Taylor, K. J.(1988). Statistical study of pit propagation

in carbon steel under nuclear waste disposal

conditions. British Journal of Corrosion,23(3), 157-164.

10.Mellan, I. (1977). Industrial SolventsHandbook. Park Ridge, NJ: Noyes DataCorporation.

11.Pourbaix, M. (1974). Atlas ofElectrochemical Equilibria in Aqueous

Solutions (2nd). Houston, TX: National

Association of Corrosion Engineering.

12.Shoesmith, D. W., King, F., and Ikeda, B.M. (1996). The indefinite containment of

nuclear fuel wastes. Materials ResearchSociety Symp. Proc., 412, 563-570.

13.Shoesmith, D. W., Ikeda, B. M., and King,F. (1992). Effect of radiation on the

corrosion of candidate materials for nuclearwaste containers. Materials Research

Society Symp. Proc., 412, 563-570.

14.Stonehouse, A. J., and Beaver, W. W.(1965). Beryllium corrosion and how to

prevent it. Materials Protection, January,24-28.

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Modeling of Beryllium Corrosion Anrc9930 1999