-166-

*

Institute of Materials Engineering, National Taiwan Ocean University, Keelung, 20224, Taiwan., Republic of China.

**

Department of Engineering and System Science, National Tsing-Hua University., Hsinchu, 30050, Taiwan, Republic of China.

166 177 90 12

Journal of Chinese Corrosion Engineering, Vol.15 No.4, PP166~177(2001)

304 200~400 NaCl

The Corrosion Behavior of 304 Stainless Steel at 200~400 in NaCl-

containing Atmospheres

P. C. Liu*, C. C. Yu*, W. Kai*, and J. J. Kai**

304 200 ~ 400

NaCl 304

Fe2O

3

NiCr2O

4Ni(ClO

4)- 2.6H

2O Fe

2O

3 Fe

3O

4 FeCr

2O

4FeCl

3-

nH2O Fe

2O

3 Fe

3O

4 FeCr

2O

4FeCl

3-2H

2O FeCl

3-6H

2O

304

ABSTRACTThe atmospheric-corrosion behavior of SUS304 stainless steel was studied over the

temperature range 200~400 in a simulated NaCl-containing environment. In general, the results

showed that the corrosion kinetics of the base metal, weld metal, and heat-affected zone obeyed

the parabolic rate law. The corrosion rate increased with increasing temperature. The corrosion

rate of the heat-affected zone were faster than other parts. The corrosion products formed on the

base metal consisted of Fe2O

3, NiCr

2O

4, Ni(ClO

4)-2.6H

2O, on the weld metal consisted of Fe

2O

3,

Fe3O

4, FeCr

2O

4and FeCl

3-nH

2O, and on the heat-affected zone consisted of Fe

2O

3, Fe

3O

4, FeCr

2O

4,

FeCl3-2H

2O and FeCl

3-6H

2O. The formation of different chlorides is responsible for the various

corrosion rates.

Keyword: SUS 304, base metal, weld metal, heat-affected zone (HAZ), kinetics

-167-

90 12

[1~2]

NaCl [3~4]

Cl- Na+

150 ~300

SUS304

304ss

304ss

submerged are welding, SAW

two passes -1

800 0.5~1.0g

3

hot plate 120

2mg/cm2

NaCl

88 100%

NaCl

200~400 [12]

200c.c./min

88

NaCl

W/A t

SEM

X -

X-ray maps X-

XRD

-168-

304 200~400 NaCl

-1 -1

-2

200

0.52 300

0.45 400

0.22 200

0.67

300 0.81 400

0.55

200

0.07 300

0.14 400

0.04

-2 304ss NaCl

-2(a)

200 2215 -2 (b)

300 939 -2 (c) 400

492 -2

-3 304ss NaCl

200~400

XRD 200

300~400

-4 (a) 304ss 200 2048

-4 (b) 400 1367

-4 (a)

-4 (b) (a)

-5 304ss NaCl

200 ~ 400

XRD

-6 304ss 400

508

-7 304ss NaCl

200 ~ 400

200

300 ~ 400

-8 (a) 304ss 300

388 X-

NaCl

Fe2O

3Fe

3O

4

-8 (b) 304ss 300

1642 X-

Fe2O

3Fe

3O

4

-8 (c) 304ss

400 652 X-

NaCl Fe2O

3

NiCr2O

4 Ni(ClO

4) -2.6H

2O

-9 (a) 304ss 200

677

9 (b) 9 (c)

-10 (a) 304ss 200

1354 (b)

(b)

304ss NaCl

[5]

304ss

[6]

NaCl

[7]

Wang

[8~9]

oxychloridation

2NaCl(s)

+2Fe(s)

+2O2(g)

Fe2O

3(s)+Na

2O

(s)+Cl

2(g)------ (4-1)

Na2O Fe

2O

3 Cr

2O

3

2NaCl(s)

+2Fe(s)

+2O2(g)

2NaFeO2(s)

+ Cl2(g)

---------- (4-2)

2Fe(s)

+ 3Cl2(g)

2FeCl3(l,g)

--------------------------- (4-3)

Fe(s)

+ Cl2(g)

FeCl2(l)

---------------------------------- (4-4)

X-ray

[7] /

304ss

1. 304ss NaCl

2.

3.

Fe2O

3 Fe

3O

4 FeCr

2O

4

-169-

90 12

FeCl3-2H

2O FeCl

3-6H

2O

Fe2O

3 Fe

3O

4 FeCr

2O

4FeCl

3-

nH2O Fe

2O

3 NiCr

2O

4

Ni (ClO4) -2.6H

2O

892001FCMA002

1. ASM, Metals Handbook, 9th Edition Vol.13 (1988)

P.80.

2. , , 100 (1995) P.42.

3. , , Vol.8 No.3

(1994) P.156.

4. , 84

, (1995) P.201.

5. Howard B. Cary, Mondern welding Technology, 3rd

edition (1994) P.454.

6. T. Valand, Corrosion Science, Vol.9 (1969) P.577.

7. H. J. Grabke, E. Reese, and M. Spiegel, Corrosion

Science, Vol. 37 (1995) P.1023.

8. Chaur-Jeng Wang and Tzong-Hann Twu, Journal of

Chinese Corrosion Engineering, Vol.9, No.4, (1995)

P.225-237.

9. Chaur-Jeng Wang and Hsum-Chou Liu, Journal of

Chinese Corrosion Engineering, Vol. 11, No.3,(1997)

P.105-119.

10. ,

(1996).

11. ,

(1998).

-170-

304 200~400 NaCl

- 1 304 ( wt.%)

Table 1. Chemical compositions (wt%) of the SUS304.

304

(wt%)

Si Mn P Ni Cr Mo

0.425 1.37 0.023 8.26 19.0 -

V Al Ti Nb Cu W

0.112 0.005 0.006 0.001 - -

Co Sb Sn Zn N Fe

0.031 0.005 0.002 - 0.033 Bal.

304

(wt%)

C Si Mn P S Cr

0.03 0.64 1.57 0.018 0.009 19.2

Ni

9.3

304

(wt%)

C Si Mn P S Cr

0.02 1.32 0.42 0.02 0.02 18.6

Ni

8.1

12. ,

(2000).

-171-

90 12

- 2 304 NaCl 200 400

( g2/cm4/sec )

Table 2. Corrosion rate contants of the SUS304 at

various experimental conditions.

200 1.96 x 10-14

300 2.95 x 10-14

400 7.56 x 10-14

200 6.50 x 10-14

300 2.46 x 10-14

400 3.50 x 10-13

200 2.27 x 10-14

300 3.80 x 10-14

400 9.90 x 10-14

200 1.05 x 10-13

300 2.46 x 10-13

400 3.50 x 10-13

200 2.06 x 10-13

300 3.88 x 10-13

400 5.45 x 10-13

200 2.42 x 10-13

300 5.40 x 10-13

400 5.93 x 10-13

- 3 PCl2

Table 3. The calculated partial pressures of chlorine.

P Cl2(atm)

200 3.01 x 10-18

300 8.90 x 10-14

400 1.17 x 10-10

(a)

(b)

(c)

-1 304 (a) (b) (c)

NaCl 200 ~

400

Fig. 1. Corrosion kinetics of (a)the matrix, (b)the

welded, and (c)the heat-affected zone for the

SUS 304 at 200 ~ 400 .

-172-

304 200~400 NaCl

(a)

(b)

(c)

- 2 304ss

(a) 200 2215

(b) 300 939 (c) 400 492

Fig. 2. Topographs of the heat-affected zone of 304ss

without NaCl-coating, (a) at 200 corroded

for 2215hr, (b) at 300 corroded for 939hr, (c)

at 400 corroded for 492hr.

1 m

1 m

1 m

(a)

(b)

(c)

- 3 304ss

(a) 200 677 (b)

300 388 (c) 400 327

Fig. 3. Topographs of the HAZ of SUS 304 with

NaCl-coating, (a) at 200 corroded for 677hr,

(b) at 300 corroded for 388hr, (c) at 400

corroded for 327hr.

5 m

5 m

5 m

-173-

90 12

(a)

(b)

- 4 304ss

(a) 200 2048 (b)

300 1367

Fig. 4. Topographs of the welded of SUS 304 without

NaCl-coating, (a) at 200 corroded for

2048hr, (b) at 300 corroded for 1367hr.

90 m

300 m

(a)

(b)

- 5 304ss

(a) 200 1354 (b) 300

1642 (c) 400 1471

Fig. 5. Topographs of the welded SUS 304 with NaCl-

coating, (a) at 200 corroded for 1354hr, (b)

at 300 corroded for 1642hr, (c) at 400

corroded for 1471hr.

20 m

30 m

(c)10 m

-174-

304 200~400 NaCl

(a) 2 m

(b) 10 m

(c) 10 m

- 6 304ss 400 508

Fig. 6. Topograph of the SUS 304 without NaCl-

coating at 400 corroded for 508hr.

- 7 304ss

(a) 200 559 (b) 300

559 (c) 400 652

Fig. 7. Topographs of the scales formed on the SUS

304 with NaCl-coating corroded, (a) at 200

for 559hr, (b) at 300 for 559hr, (c) at 400

for 652hr.

30 m

-175-

90 12

(a)

(b)

(b)

(c)(c)

- 8 X- (a) 304ss

300 388 (b)

304ss 300 1642

X- (c) 304ss

400 652

Fig. 8. XRD analyses of the scales formed on the HAZ

of 304ss with NaCl-coating (a) at 300 for

388hr, (b) at 400 for 1642hr, and(c) at 400

for 652hr.

- 9 (a) 304ss 200

677 (b) Fe

(c) O

Fig. 9. (a)Cross-sectional micrograph of the HAZ of

304ss corroded at 200 for 677hr, (b)the

corresponding Cl-map, and(c)O-map.

(a)5 m

-176-

304 200~400 NaCl

10 (a) 304ss 200 1354

(b) Cl

Fig. 10. (a) Cross-sectional micrograph of the welded

304ss corroded at 200 for 1354 hr, (b) Cl-

map.

(b)

(a) 5 m

-177-

90 12