Issuu on Google+

Q/


ORNL/ zms- 57 8 2

C o n t r a c t N o . W-7405-eng-26 METALS

The Corrosion Resis

G E W I C S D-fVLSPQN

of

J. R. Keiser, J. H. D

Date Published

316 Stainless S t e e l t a L i z n, and D. L. Manning

- April

1977

QPlCE This document contains information of a preliminary nature. It is subject to revision O F correction and therefore does not represent a final report.


.......................... ............................ ....................... ....................... ........................... ..............................


THE CORROSION RESISTANCE OF TYPE 396 STAINLESS STEEL TO Li2BeFb nd D. LI.M a

J . R. K e i s

orrela t e d

WI

A corrosion e as-recei

was observ

a l t further

blanket mat

t-

eactors w i l

a t i o n of n e u t h fabrication,

roduction of

nl.ess s t e e l

have r e s u l t

t-wall. mate

i o n f o r the

ket capable

are limite

CI

k e s material

b e a r i n g eompa

e

Because

may impose

t, s t r o n g c o n s i d e r a t i

1.

8

re


2 t h e s a l t s TdiF and BeF2 f o r a b l a n k e t of a f u s i o n r e a c t o r w i t h a s t a i n l e s s

s t e e l f i r s t wall.

The p u r p o s e of t h i s paper i s t o r e p o r t on t h e c o r r o s i o n

r e s i s t a n c e of t y p e 316 s t a i n l e s s s t e e l t o %i2BeFt+.

There are p o t e n t i a l problems a s s o c i a t e d w i t h t h e u s e of Li.F-BeF2 as a combined c o o l a n t - b r e e d i n g material.

These i n c l u d e t h e e f f e c t i v e

b r e e d i n g and t h e e f f i c i e n t r e c o v e r y of t r i t i u m , t h e e f f e c t on t h e salt:

of induced e l e c t r i c f i e l d s and o f t r a n s m u t a t i o n p r o d u c t s , and t h e compatib i l i t y of t h e s a l t w i t h t h e component i t c o n t a c t s .

The % r i t i . u m b r e e d i n g

r a t i o of t h i s s a l t i s n o t a s h i g h as i s t h a t of l i t h i u m , and some d e s i g n s would probably r e q u i r e t h e a d d i t i o n of a n e u t r o n mml..ti-plier such as beryllium. A n o t I i e ~problem coul-d b e t h e e l s c t ~ i f~i .e l d induced i n t h e c ~ n i d u c t i n g

s a l t when

i t

containment

f l o w s through t h e i n t e n s e magnetic f i e l d s r e q u i r e d f o r plasma T h i s p o t e n t i a l d i f f e r e n e e o c c u r r i n g hetwcen the salt and

t h e p i p e wall could b e g r e a t enough to e l e c t r o l y z e t h e salt and t h u s

cause s e v e r e c o r r o s i o n problems f o r the metallic c o n t a i n e r

e

Means OP

r e d u c i n g the e f f e c t of t h e induced f i e l d to a t o l e r a b l e level. have been s u g g e s t e d by Horneyer.

According t o him, e l e c t r o l y t i c c o r r o s i o n could

b e minimized by a v o i d i n g , a s much as p o s s i b l e , h i g h f l u i d v e l o c i t i e s

p e r p e n d i c u l a r t o t h e magnetic f i e l d .

Solution of t h i s problem w i l l

most probably have t o b e a r e s u l t of e n g i n e e r i n g d e s i g n changes r a t h e r

t h a n through a d d i t i o n s or m o d i f i c a t i o n s t o t h e s a l t ,

An a d d i t i o n a l c o n c e r n w i l l be t h e c o r r o s i v e e f f e c t of t h e salt on A s seen from t h e f r e e e n e r g i e s of formati-on in

the. s t a i n l e s s s t e e l .

T a b l e 1, L i F and BeF2 a r c much more s t a b l e t h a n t h e f l u o r i d e s of the major c o n s t i t u e n t s of s t a i n l e s s s t e e l , E e , Ni, and Cr.

Consequently,

no s i g n i f i c a n t r e a c t i o n of t h e s a l t components w i t h the m e t a l l i c c o n t a i n e r i s e x p e c t e d ; however,

i m p u r i t i e s i n the s a l t may cause c o r r o s i o n ,

t i e s expected t o b e p x c s c n t a r e HP and N i F 2 ,

Impuri-

and t h e s e w i l l c a u s e

r e a c t i o n s of the? t y p e :

2W. R. G r i m e s and S t a n l e y Carter, “MoPten Salt Blanket F l u i d s i n C o n t r o l l e d Ftasion R e a c t o r s pp 161--9(4 i n The Chemistry of Fusiovi TechnoZogy D. M. Gruen, e d . Ylenan P r e s s , New York, 1972.

3W. G. Horneyer

flTherrnal and Chemical A s p e c t s of t h e Thernnoniiclear

Blanket Problem,� T e c h n i c a l Report 4 3 5 , M. 1, T . Research L a b o r a t o r y of

E l e c t r o n i c s (1965).

,


3

T a b l e 1.

Foma

of F l u o r i d e

LiF

-448

-107

---e,10

---98

@rFz

-7 5

FeF2

--67

HF

-66

NiF2

-5 5

MOF6

-5 0

aC. F , B dynamics of M 15, 6 2 4 , P , C

MF2

+

Cr

ions of i m p u r i I l y b u t w i l l s1

o additional.

690801 (196’3)

e

ould be Ni o ntainer w i l l i m p u r i t i e s are

d t o t h e system, a a r e not exp

hours these

of a r e d u e t

e t h e corrosive

p u r i t i e s by s.

n e u t r o n react e of o x i d a n t s in t

The t r a n

r e p r e s e n t axlo e

elemental

C8

are expected


T h e reactions o f l i t h i u m ,

7LiF

4-

n

3

-f

H e -E. ,WF f n c

(3)

are, of c o u r s e , d e s i r e d became t h i s is thc means of p r o d u c i n g t h e

tritium f u e l .

Hocdcver, t h e TF p ~ o d ~ ecan d react w i t h t h e s t a i n l e s s

steel. c o n t a i n e r t o form metals f l u o r i d e s as shown i n ~ q (1). .

Transmutation of b e r y l l i u m c a n occur i n either of

6

The ,Ke undergoes beta decay w i t 1 1 an O.$-sec

~ W Q ways:

h a l f - l i f e yir?l.di.ng f a r t h e

r i g h t s i d e of Kquation 6,

‘The f l u o r i n e produced i n these beryll.ium t r a n s m u t a t i o n reac t i a n s

can react w i t h t h e s t a i n l e s s s t e e l c o n t a i n e r , c o n s t i t u t i n g a n o t h e r source of c o r r o s i o n .

The o t h e r t r a n s m u t a t i o n of t h e s a l t cornponents i s that o â‚Ź f l u o r i n e :

The

16

,N

-~undergoes

beta d e c a y w i t h a b o u t a 7-sec ha8f-l.ife

yielding

16

0,

which can be expected to r e a c t w i t h t h e containment metal c a u s i n g a d d i tional. c o r r o s i o n .

The net r e s u l t of all.. three tuansrnritation r e a c t i o n s

i s the product.i.on o f s u b s t a n c e s that w i l l cause ear-rosion of t h e s t a i n l e s s


5 s t e e l containment a l l o y nt and p o s s i b

One means of

p s o f clliminat-ing t

. T2

this c o r r o s i o n

This buffer

and a s o l u b l e f

01pre.s i n s a l t and can

One o t h e r problem a

tritium from the s a l t ,

in the form of Tz bec

b l y make i t e:

o b e c a p a b l e of (

cting with the f I t of the s a l t .

t h e u s e of LizBe

the recovery

8

er r e q u i r e d t o

ity of TF w i t h s t a i n l e s s s t e e l

the tritium f r

and tritium

me

r i f a CizBeFt, b sel,

n-

A great de

redox b u f f e r h a s been a

with molten s

as a r e s u l t of work f a r t h e

The f u e l salt

e n S a l t Breeder R e sed of L i F and E3

f e r t i l e mat

Cause of r e x . h preparation

i s a c t u a l l y fou

e containment

i n both t h e her t h e s e compo

of t h e f u e l t addition of

a w e serious

f an o x i d i z i

t sf material

containment

s i n some U ( I I

nd, converse1 of U ( I V ) to

u

11) r a t i o migh

t i c swings in th

a

se of t h i s b e n t i a 1 w i l l . take

6

reactor


6

t h a t c o u l d make t h e s a l t s u f f i c i e n t l y "reduciiig'l t o p r a c t i c a l l y e l i m i n a t e t h e c o r r o s i o n caused by i m p u r i t i e s and t r a n s m u t a t i o n p r o d u c t s is beryllium,

Typical. r e a c t i o n s c o u l d be:

To d e t e r m i n e t h e s u i t a b i l i t y o f s t a i n l e s s s t e e l f o r c o n t a i n i n g Li2BeF4, c o r r o s i o n measurements have been made w i t h sa1.t i n t h e a s - r e c e i v e d c a n d i t i o n and i n t h e r e d u c i n g c o n d i t i o n reached by a d d i n g b e r y l l i u m t o it EXPERIMENTAL METHODS

The e x p e r i m e n t a l assembly used f o r t h i s c o ~ r o s i o nwork, cal.l.ed

a thermal-convection

l o o p , i s shown in F i g . 1.

The l o o p p o r t i o n of

t h e assembly i s c o n s t r u c t e d of t y p c 316 s t a i n l e s s s t e e l t u b i n g and i s h e a t e d on t h e bottom and one v e r t i c l e s i d e .

Cooling t h e o t h e r t w o

s i d e s c a u s e s t h e m o l t e n s a l t i n t h e t u b i n g to f l o w because o f t h e v a r i a t i o n i n d e n s i t y of t h e salt w i t h temperature,

the s a l t i s about 1 m l m i n ,

The v e l . o c i t y of

Other i m p o r t a n t f e a t u r e s of t h e I S O ~ are

t h e removable c o r r o s i o n specimens and t h e accesses f o r i n s e r t i o n o f

e l e c t r o d e s f o r voltammetry measurements and f o r a d d i t i o n of material to t h e s a l t i n t h e I-oop o r removal of salt samples from t h e 100p.

S i x t e e n c o r r o s i o n specimens a r e

IISFZ.w ~ ,i t h

e i g h t i n s e r t e d i n the h o t

l e g (heated v e r t i c a l s e c t i o n ) and e i g h t i n t h e c o l d keg ( c o o l e d verticle section).

T h es e specimens a r e removed from. t h e l o o p e v e r y

500 h r f o r weighing and examination..

When t h e irivestigationas t o b e

made w i t h a p a r t i c u l a r s e t s f spcci.rnens a r e completeds s e v e r a l of the speci.mens a r e examined m e t a l l o g r a p h i c a l l y a n d , i f b7arwanted

electron m i c r o p r o b e .

w i t h the

These r e s u 1 . t ~reveal at which t e m p e r a t u r e w e i g h t


7

ORWL-DWG

68-598TR3

SAMPLER

1

FLUSH

TANK

1

I

TANK

ion t


8

g a i n s o r l o s s e s have occi.mred, and t h e microprobe examination i d e n t i f i e s which components of t h e specimen material. have been t r a n s p o r t e d ,

One of t h e most s i g n i f i c a n t improvements i n thermal-convec t i o n

l o o p operation h a s been the a p p l i c a t i o n of v o l t a n m e t r y

potential volta

e

Controlled-

e t r y i s a modern e l e c t r o c h e m i c a l t e c h n i q u e , w1-nicl-n

may be used t o examine t h e n a t u r e of an electrochcnaical r e a c t i o n i n d i f f e r e n t media, such as aqueous and nonaqueous s o l u t i o n s a n d highFor measurements i n mol.ten L ~ ~ B E F, Ithe .~

t e m p e r a t u r e salt systems *

electrodes c o n s i s t e d of the 1 . 0 0 ~i t s e l f , which s e r v e d as the c o u n t e r

e l e c t r o d e , and two i r i d i u m e l e c t r o d e s , which were the quasi-refermce

and working e l e c t r o d e s .

These e l e c t r o d e s were t y p i c a l l y 25-nm

l e n g t h s of 1.8-gage i r i d i u m wires welded t o 3-mm-OD (118-in.)

risers.

TIE

(1-in.)

ni-ckel

e1.ectrode area exposed t o the m e l t was 10 t o 20 m m 2 -

T R ~

voltammograms were ~ e c ~ r d eversiis d the i r i d i u m qziasli-reference e l e c t r o d e

(IK QRE), which i s p o i s e d a t t h e equi.l.ibrium p o t e n t i a l (Eeq ) of t h e

melt.

I n this mamner rel.atiwe chan.ges i n t h e o x i d a t i o n p o t e n t i a l . o f

t h e s a l t anid of t h e c o n c e n t r a t i o n of c e r t a i n i m p u r i t i e s and p r o d u c t s c a n be measured o n - l i n e .

COKI-OS~CIII

The e q u i l i b r i u m p o t e n t i a l o f t h e

s a l t is a measure of the tendency of t h e m e l t t o r e a c t w i t h o x i d i z a b l e

materials t h a t i t c o n t a c t s .

For m e l t s that a r e n o t p o i s e d by a redox

b u f f e r r e l a t i - v e changes i n t h e equiSi.briurr1 p s t e , n t i a l a r e c o n v e n i e n t l y observed by determining v o l . t a m e t r i c a l - I * yt h e potential d i f f e . r e n c e (AE)

between t h e m e l t e q u i l i b r i u m potential.. and t h e c a t h o d i c l i m i t of t h e

melt, which f o r E ~ ~ B ~ iFs Lthe , r e d w t i . o ~ nof b e r y P l i u m ( I 1 ) .

We d e f i n e

t h e c a t h o d i c l i m i t f o r these measurements a s t h e p o t e n t i a l a t 80 n ~ 4

c e l l current.

Other r e f e r e n c e markers may a l s o b e used as l o n g a s t h e

same c o n d i t i o n s a r e m a i n t a i n e d ,

A d e c r e a s e i n A&’, r e s u l t i n g i n a

c a t h o d i c s h t f t i n Eeq f o r example, indicates that t h e melt h a s beconlle l e s s o x i d i z i n g ; and a n i n c r e a s e i n AI7 i n d i c a t e s t h a ~t h e o p p o s i t e h a s occurred

A voltammetric s c a n t h a t shows t h e c a t h o d i c l i m i t r e l . a t i v e

t o Eeq i s i1l.usltrated i.n F i g . 2,


9

80

60

40

20

F i g , 2.

L i 2BeF4 i n I,

n Final L i m i t

r e d u c t i o n of

mmogram shown i n

h e i g h t s of t h e t w o waves

t o about 1 3 r e s u l t s of a v o l t a m m e t r i

due t o i r o n has

the same h e i g h t .

It is a

k potential of

eral weeks a f t e r that

le the chro

t o note t h a t cathodic shif

of t h e analyse

tential v o J t a


1.0

Fig. 4 *

Reduction. of Chromium in Loop NCL 31,


11

16 stainless

were f i r s t exp

"on loop cont

t a i n l e s s stee

190 ppm Fe, 60 e of 650째C and 500 and 1000 ans of v o l t a

,a

Following thi

.

It and a n e

beryllium

t a i n l e s s steel

These s p e c i

ng af t h e cond n a t i o n of t h e

h e f i r s t 500

t significant

d occurred, m

b e c a u s e of r e a c t i o n s with

.

F i g u r e 5 shows t

st and l o w e s t temp


12 weight l o s t by t h e h o t t e s t specimen d u r i n g t h e f i r s t 508 h r , i f w e assume t h a t t h e material w a s l o s t u n i f o r m l y f r o m t h e s u r â‚Ź a c e ,

c o r r e s p o n d s t o a c o r r o s i o n r a t e of a b o u t 10 ym ( 8 . 4 m i l ) p e r year.

ow ever, i n p r e v i o u s W Ow~i t P h s t a i n l e s s steel i n fluoricie salts

c o n t a i n i n g U F 4 as an o x i d i z i n g s p e c i e s , c o r r o s i o n d i d n o t r e s u l t i n uniform removal of material; r a t h e r , a porous s t r u c t u r e w a s found (Fig. 6 ) .

The 1000-hr e x p o s u r e of

OUT

specfinens w a s n o t l o n g e n ~ i ~ g l i

f o r e x t e n s i v e c o r r o s i o n t o occur, b u t F i g . 'I i n d i c a t e s that material w a s n o t removed u n i f o r m l y from t h e h o t t e r specimen.

Consequently, t h e

d e p t h of a t t a c k c a n b e expected t o exceed that c a l c u l a t e d f o r uniform m a t e r i a l removal.

Futhermore, i n t h e s a l t of a f u s i o n r e a c t o r , impuri-

t i e s would b e p ~ o d u c e d c o n t i n u o u s l y and i n s i g n i f i c a n t q u a n t i t i e s , and these i m p u r i t i c s would be m u r e o x i d i z i n g t h a n t h e i m p u r i t i e s found i n t h i s experimental s a l t .

Thus, c o r r o s i o n of s t a i n l e s s s t e e l i n a

L-usion r e a c t o r coiz'hd b e a s e r i o u s prohl-cm i f no e f f o r t i s made t o buffer the salt.

Y-'3 277


13 Y- 134722

. 7.

Type 316

TO e v a l u a t e t h e e f f e c t i2BeF4, a p i e c e o

wed t o r e a c t .

As s

cally, indicating

ts i n d i c a t e d t A new s e t of Examination w e i g h t chan

e w e i g h t changes f a smaller f o r t h e s

ecimens Expos

r on t h e c o x r o s s inserted i n t

e equilibrium made l e s s o x i d i t i o n t o be les ed t o t h i s r e

ter 500 and of d e t e c t i o n .

en temperatu he reducing s

h r than i n t F i g u r e 5 shows t h a t o t h e f i r s t 500-

ium w a s removed from

e t o the red

n the hottest

increasing we

f time.

Thi

c u r r e d becaus

urn w a s remov

the salt wer

urn and t h e sa

i v e l y more ox

n a low corr continuously o r a t least e of t y p e 316 s t a i n l .

a range acceptable f o r f

ium would have

If t h a t were done eF4 s a l t c o u l d b e


14 ORNL-DWG

-4.1 5

77-3822

- 1.10 >

0

v

d 5 -4.05

t-

z

w

)-.

B

t 5 J-.

-1.00

-0.95

<

-----e-

-0.90

0

t

Be ADDITION

20

4Q 60 TIME (days)

400

F i g . 8. V a r i a t i o n of the L i m i t f o r TAZBeFb S a l t i n NCL 3 1 . CONCTAJS IONS

The c o n c l u s i o n s t h a t can be drawn from t h i s r e s e a r c h are:

1.

The o x i d a t i o n p o t e n t i a l o f t h e s a l t can be c o n t r o l l e d by

a d d i t i o n s o f a r e d u c i n g metal, 2.

V o l t a m e t r i c t e c h n i q u e s p r o v i d e o n - l i n e measurement o f the

o x i d a t i o n p o t e n t i a l of t h e s a l t and t h e c o n c e n t r a t i ~of ~ ~i m p u r i t i e s i n the salt.

3.

High c o r r o s i o n r a t e s a r e encountered i n i t i a l . 1 - y i n s a l t w i t h

a normal i m p u r i t y c o n c e n t r a t i o n .

4.

The c o r r o s i o n r a t e of t y p e 316 s t a i n l e s s s t e e l i n Li2ReF1,

s a l t w a s reduced s i g n i f i c a n t l y by t h e d i r e c t a d d i t i o n of b e r y l l i u m metal t o t h e s a l t ,


95

T h e a u t h o r s would

Soar o p e r a t i n g t h e thermal-c * ing, S. Peter n o f t h e manu

e f f o r t s of E . S. Lawrence DJStefano and J . L. Scott 1 G 0 1 l . i h e ~f o r f i n a l e


17

IBUTION 1-2

.

3. 4. 5.

6. 7.

8.

11

.

12. 13.

16.

17 * 20

21. 22.

23. 23.

C e n t r a l Research L i Document Referen Laboratory Rec o r a t o r y Rec L Patent O f ?A. G . Alsmiller S . Bettis H. Bryant D. Cannon J. F. Clarke R, E. Clausing S I D. Clinton E. Cunningha a A* Dandl J. H. DeVan P. F r a a s sion Energy D sion Energy D A. Gabriel M. L , Grossbeck P . M. Haubenre M, R. Hill J. A. Horalc

. .

.

O f f ice

64, 65. 66. 67.

W.C.T.

J , S, W J. R, W

W. M, Wells

EXTERNAL DISTRIBUTION

70-71,

ARGONNE NATIONAL L

0 South Cass Avenue, Argonne, IL

V. A. Maroni, CTR Program, 208 Wl15 D. L. S m i t h

7 2. 73-74.

CULHAM IABOMTORY,

n, 0x14 3DB, Un

PRINCETON PLASMA P

ORY, P.O.

m

Box 4 5 1 , P

R. M i l l s

W, G. P r i c e 75.

PRINCETON U N I V N J 08540

E. Johnson

E n g i n e e r i n g De

tmen k , P r i n c e t o n 9

60439


1.8

76.

WESTINGHOUSE ELECTRIC COKPQKATPON, R e s e a r c h and D e v e l o p m e n t C e n t e r , Yittsburg, PA

1.5235

R. E. Gold

77-82!

. I

E W A D I V I S I O N OF MAGNE'X'IC F U S I O N ENERGY

Washington, DC

20545

M. M. C o h e n E , N . C . Dalder C. R. F i n f g e l d T. C . R e u t h e r , J r . J . M. W i l l - k r n s K. M. %,wil.sky

83-84,

ERDA,

OAK KIDGE OPERATIONS OFFICE, P.O.

Box E , Oak R i d g e , TN

37830

D i r e c t o r , Reactor D i v i s i o n D i r e c t o r , R e s e a r c h and Technical S u p p o r t D i v i s i o n

85-11.1. ERDA TECHNICAL INFORMATION CENTER, O f €ice of Technical Information, P.O. Box 62, Oak R i d g e , T N 37830

P


ORNL-TM-5782