in Liquid Li and Pb-Li Review of Structural Material Corrosion · 2016. 6. 26. · iron-based heat transfer systems – For Vanadium-based systems Nitrogen inhibits ... m/yr at 700

SS-NG: Nov.'00 APEX-SNL 1

Review of Structural Material Corrosionin Liquid Li and Pb-Li

S. Sharafat and N. M. Ghoniem

The University of California at Los Angeles (UCLA)Los Angeles, CA. 90095-1597, USA

APEX Meeting

Sandia National Laboratory

November 15-17, 2000


OUTLINE

• Liquid metal corrosion examples

• Review in conjunction with Na-Steel Data effects of:– Velocity, Tmax, ∆T, Impurities– Product deposition rates– Rate of Temperature Rise– Coatings

• Systems:– Steel-Lithium – V-Lithium

– Steel Pb-Li– V-Pb-Li

• Summary


Examples of Liquid Metal CorrosionMOLTEN LEAD:T = 700oC∆T = 150oCV = 3 cm/s

ALLOYS:• Hasetlloy:

– 70% Ni; – 8000 ppm at 700oC

• Croloy: – 2NL

QCr, 1Mo, 0.5Mn;

– 8 ppm at 700oC

• Fecralloy: – 15Cr, 4Al

• Meehanite: – cast Fe, 3C, 1Si

R. C. Asher et al., 1977


Example of Lithium-Steel Corrosion

• Formation of a ferritic layer on 316 SS:

– Leaching of Cr, Ni, and Fe

• Nitrogen solubility in Li is high even at Tm (~1000 ppm):

– Nitrogen must be removed for iron-based heat transfer systems

– For Vanadium-based systems Nitrogen inhibits certain corrosions

• Austenitic 316 Stainless Steelin Li:

Tmax = 425oCN = 200 -500 ppmt > 3000 hr

R. C. Asher et al., 1977


Corrosion Damage Zones• Corrosion is often

described in terms of a simple mass loss rate:– Mass loss rate

(g/m2-year), or– Surface recession

rate (µm/year)

• However, 3 processes constitute corrosion:– Surface Regression

(wall thinning)– Surface Degradation– Intergranular attack

(IGA)

Examples of corrosion damage in SS (8000 h, Na:700oC, high ∆T)

J.H.DeVan, 1985

Total Damaged Zone


Liquid Metal Corrosion Issues• Two major compatibility concerns:

• (a) Corrosion/Mass transfer• (b) Degradation of mechanical strength

• Corrosion, uniform or selective dissolution and/or intergranular penetration can result in:

• wall thinning (mechanical strength)• corrosion products can restrict flow (pumping power)

• Near-surface deformation behavior through:• Liquid metal embrittlement (LME)• Oxidation, nitridation, or carburization-decarburization

• Bulk properties are affected by:• Compositional and microstructural modifications.• Selective corrosion, interstitial-element transfer, and/or thermal

aging.

• Most experience exists with LMFBR Na-Steel systems


Experience with Li-Corrosion of Austenitic and Ferritic Steels

• Li and Pb-Li: Static, Thermal-Convection-Loop (TCL; v=0.05 to 0.3 m/s), and Forced-Circulation-Loop (FCL; 0.3 to 4 m/s)– (a) Austenitics develop ferritic layer (depletion of Ni and Cr)– (b) Ferritics show little or no surface degradation– (c ) Intergranular penetration with (> 1000 ppm N) in both

• Existing experimental data are insufficient to accurately establish corrosion behavior:– Experiment parameters vary significantly:

• Velocity, ∆T, Area, and Purity


ApproachLiquid Na corrosion has been studied extensively since the late 1940s

• Augment Li corrosion understanding by Na-data

Solubility of Metals:

– In the absence of (O, N, C) dissolution of metals (except Al) is very low, unless driven by large ∆T in the loop.

Sodium Lithium Lead-Lithium Lead-bismuth(wppm @ 400 C) (wppm @ 400 C) (wppm @ 400 C) (ppm @ 500 C)

Fe 0.04 0.94 35 2.3Cr 9x10-5 0.9 5 11Ni 0.55 56.8 2360 25000V low 0.008 low -Ti low low low 300Mo 0.25 0.25 0.1 (Pb,700C) -W low low 0.1 (Pb,700C) -Al 24.2 4x105 2000 -


SS-Na Velocity Correlations

• SS-Na: Velocity and Oxygen were identified as the two major variables:– Statistically corrosion rates were

independent of velocity above 3-4 m/s

– Corrosion rates were found to be directly proportional to oxygen concentration.

For V> 4 m/s (1ppm O):R = 1.69x109exp(-18120/TK) µm/year

For V< 3 m/s (1ppm O): R = (2.97x108 + 2.91x108 V)

exp(-18120/TK) µm/yearNa-corrosion rate of 316SS at 1 ppm O

(afer J. H. Devan, 1985)

1000/T(K)1.11.21.31.4 1.0

Cor

rosi

on R

ate

(µm

/yea

r)

0.01

0.1

1

10 ||||||450 500 550 600 650 700 (oC)

VELOCITYINDEPENDENT(V > 3 m/s)

VELOCITY DEPENDENT(V = 1 m/s)

Bagnall, 1975


SS-Li Velocity Correlation (?)

• System parameters affecting corrosion rates of ferrous alloys in Li are much more varied.

• Nitrogen effects are complex:– In static tests: below 500oC

significant weight loss even with low N levels (20-50ppm).

– Dynamic tests: above 500oC “nil” weight loss even with high N levels (500 ppm).

• Can not develop similar correlations for Steel-Li as for Steel-Na.

Corrosion rates of 304 and 316 SS after 1500 h

0.1

1

10

100

1 1.1 1.2 1.3 1.4 1.5 1.61000/T(K)

Diss

olut

ion

Rat

e (m

g/m

2 -hr)

Whitlow, 1979Selle, 1976Rumbaut, 1981Casteels, 1981.

TCL:

FCL:

700 600 500 400 (oC)


Corrosion Product Deposition Rate

• Mass transfer affects:– IHX performance– Radiation exposure– Blockage

• Deposition rates (DR) in a Na-steel loop have been reported as a function of ∆T.

• In Li-system only one study has looked at the deposition rates (Tortorelli, ’80):

– TCL, Thot = 600oC, ∆T = 150oC,v = .03 m/s

• Initially 16-mm-diam channel was completely plugged:

– after 1000 h DR~70 g/m2-y– after 4000 h DR~30 g/m2-y

Na-304SS, v=4m/sThot=740oC, >1500 h(Shiels, 1976)

400

450

500

550

600

10 20 30Deposition Rate (g/m2-year)

Tem

pera

ture

(C)

Li-316SS600oC; ∆T=150oCV=3 cm/s, >4000 h*(Tortorelli, 1980)

15 mm


Effect of Heating Rate

• Rate of temperature change (dT/dL) in the coolant as it flows along a heated section.

• For Na a high dT/dLincreases:– Corrosion rate (Rc) in

austenitic steels– Ferrite layer thickness.

• Corrosion rate is factor of 9 larger at 250oC/m than at 40oC/m (@700oC).

Enhancement of corrosion rate for 316SS in Na, high dT/dL1000/T(K)

1.11.21.3 1.0

Cor

rosi

on R

ate

(µm

/yea

r)

0.1

1

10

100 |||||500 550 600 650 700 (oC)

T316 SS (40oC/m)

9 µm/year

1 µm/year

3 µm/year

Extrapolated on9µm/yr at 700oC(250oC/m)


Summary of Steel-Li Corrosion TestsAustenitic Steels:

304 and 316Ferritic Steels

(HT-9)

Weight Loss (mg/m2-h) W = ktn ; (n = 0.7) W is linear with time

Dissolution rates FCL 5-20 > than in TCL FCL comparable to TCL

Ferrite layer formation

TCL: 55 µµµµm/y at 570oCFCL: 100 µµµµm/y at 482oC

No internal corrosive attack (low ppm N); Slight depletion of Cr near surface

Microstructure Effects

20% cold worked has 2 times larger than annealed

Effect of ∆∆∆∆T and Velocity

Insufficient data to derive correlations for LiCorrosion (R) rates in Na increase with ∆T and Velocity

Up to 3 m/s: R ∝∝∝∝ ( 2.97 + 2.91 V)

Lithium Purity (FCL)

Weight loss with 50 ppm N is 2-5 times lower than with200 ppm N.

Findings: • N impurity plays a significant role (like O in Na).• For ferritic steels: No significant difference between TCL (v < 0.2 m/s) & FCL (v < 4 m/s) • Corrosion rate of Ferritic Steels 5-10 times < Austenitic Steels


Summary of V-Lithium Tests

Experiment Type of Test Alloy Operating

Conditions Primary Results

Pratt-Whitney ('50 - '60)

Forced-Circulation Loop

Un-Alloyed V

Velocity: 4 m/s; Exposure: 1170 h; Tmax = 870oC ∆∆∆∆T = 220oC

Corrosion rate: NIL (<0.1 mg/m2h or 0.1 µµµµm/y)

ORNL ('60) Capsule tests

High and low-purity alloys: V-15-Cr-5Ti, V-10Cr

Tmax=816oC

Corrosion rate: NIL Redistribution of Oxygen was observed; Compared with Ta & Nb only small penetration with O2

present.

ANL ('70-'80)Forced-Circulation Loop

High and low-purity alloys: V-15-Cr-5Ti, V-10Cr

Velocity: <1.5 m/s; Exposure: 500 h, & 30000 h; Tmax = 650oC ∆∆∆∆T = 150oC

Small weight changes; High-purity alloys show no degradation in tensile properties,

PRANA ('90) Russian Federation

Force-Circulation &Thermal-Convection Loop

V-4Ti-4Cr (Welds, AlN-Coated); V-10Ti-5Cr; V-9Ti-4Cr

Velocity: 4 m/s; Exposure: 1000 h; Tmax = 870oC ∆∆∆∆T = 220oC

High corrosion resistance of V-Ti-Cr alloys; N and Al increase compatibility with SS.

Findings: • No significant difference in corrosion rates between alloyed and unalloyed vanadium;• Corrosion rate of V-alloys is about factor of 1,000 lower than Austenitic Steels

and about 100 lower than Ferritic Steels.


Summary of Steel-PbLi Corrosion TestsAustenitic Steels:

304 and 316Ferritic Steels:

HT-9 and Fe-9Cr-1Mo

Weight Loss(mg/m2-h)

W = ktn

(n = 0.5-0.9; 410<T<460oC)linear at 500oC

W is linear with timeFactor of 5-10 lower than 316 SS

Lower in static Pb-Li than flowing for bothReaches constant value after 1000-3000 h

Dissolution rates 10 times larger than in Li FCL comparable to TCL

Ferrite layer formation In flowing Pb-Li develop very porous ferrite layers

Little or no internal corrosive attack

Microstructure Effects

PCA 4 times greater than annealed or cold-worked 316

Effect of ∆∆∆∆T,Velocity NO DATA REPORTED

Pb-Li purity NO DATA REPORTED

• Group V and VI refractory metals have low solubility in both Li and Pb.• Good corrosion resistance for Vanadium is predicted.• ANL scoping tests indicated no measurable corrosion of V-15Cr-5Ti after 2300 h in Pb-Li at 430oC:

– Steels have a factor of 50 higher corrosion rate in Pb-Li than in Li– Take V-alloy corrosion rate to be a factor of 50 higher in Pb-Li than in Li.

Vanadium Pb-Li


Summary of Corrosion Data in Flowing Lithium

Increasing Velocity (0 – 4 m/s)

VanadiumAlloys

FerreticSteels

AusteniticSteels

MASS TRANSFERLIMIT (remote)

20 µm/y

5 µm/y

Radioactive Mass

Transfer Limit

0.5 µm/y


Increasing Velocity (0 – 4 m/s)Vanadium

Alloys

FerreticSteels

AusteniticSteels

MASS TRANSFERLIMIT (remote)

20 µm/y

5 µm/y

Radioactive Mass Transfer Limit

0.5 µm/y

Summary of Corrosion in Pb-Li


Summary

• Corrosion rates of ferrous and refractory alloys in liquid Li saturate at flow velocities of about 5 m/s.– No data available to make similar assertion for PbLi.

• Nitrogen content must be controlled to below 50 ppm in Li for For ferrous alloys:– Addition of N and of Al minimizes corrosion rates in Vanadium

alloys.

• Deposition rates for Li-316SS have been measured to be 30 g/m2/year (∆T=150oC, Tmax=600oC, 4000 h).

• Rates of temperature-rise along heated sections might have significant impact on corrosion rates.


CONCLUSIONS

• Based on Na-Steel experience, corrosion rates saturate at aboutv=4 m/s.

• High corrosion resistance of V-Ti-Cr alloys has been experimentally confirmed in FCL (700oC, v=4 m/s, t >1000h)

– Negligible weight change.

• Bi-metallic tests with welds have shown some weight gain (0.8%) by V-Ti-Cr alloys:

– Drastic reduction of weight gain (0.4%) by adding Al (~3 wt.%) and nitrogen (500 wppm) to the Lithium

• Corrosion of refractory alloys, particularly with a ceramic coating may be negligible at blanket operating conditions.

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in Liquid Li and Pb-Li Review of Structural Material Corrosion · 2016. 6. 26. · iron-based heat transfer systems – For Vanadium-based systems Nitrogen inhibits ... m/yr at 700