Nickel Insitute - Nickel Alloys in Organic Acids & Related Compounds

TABLE XX

Corrosion of the HASTELLOY 

and Associated Alloys in Acetic Acid

Tests of 120 hours’ duration at the temperature shown.

Corrosion Rate 66 ºC (151 ºF)

25 ºC (77 ºF)

Boiling

mm/y

mpy

mm/y

mpy

mm/y

mpy

Medium

10% Acetic Acid

HASTELLoy alloy B

.01

0.5

.15

6

.02

0.7

HASTELLoy alloy C

.01

0.2

.01

0.2

.01

0.4

HASTELLoy alloy D

.02

0.6

.23

9

.05

2

HASTELLoy alloy N

.03

1

.07

2.7

.03

1.2

HAYNES* alloy No. 25

Nil

Ni l

Nil

Ni l

.00

0.1

MULTIMET* alloy

Nil

Ni l

Nil

Ni l

.00

0.1

50% Acetic Acid

HASTELLOY alloy B

.03

1

.10

4

.01

0.4

HASTELLOY alloy C

.00

0.1

.00

0.1

.00

0.1

HASTELLOY alloy D

.08

3

.46

18

.08

3

HASTELLOY alloy N

.03

1

.06

2.5

.04

1.7

Nil

Ni l

.00

0.1

HAYNES alloy No. 25

Nil

Ni l

MULTIMET alloy

Nil

Ni l

Nil

Ni l

.00

0.1

99% Acetic Acid (Glacial) HASTELLOY alloy B

.01

0.5

.01

0.2

.00

0.1

HASTELLOY alloy C

.01

0.2

.00

0.1

.00

0.1

HASTELLOY alloy D

.01

0.5

.13

5

.02

0.9

HASTELLOY alloy N

02

0.7

.02

0.7

.02

0.8

Nil

Ni l

Nil

Ni l

HAYNES alloy No. 25

Nil

Ni l

MULTIMET alloy

Nil

Ni l

Nil

Ni l

.00

0.1

*Trademark of Cabot Corporation

Reference 45

G. Iron-Base Nickel-Chromium- Molybdenum Alloys There are several proprietary alloys

H. Nickel-Base Molybdenum- Chromium Iron Alloys

of approximately 25Ni-21Cr and 4 to 6.5 per cent molybdenum that were developed mainly for resistance to localized attack such as pitting and crevice corrosion in chloride environments. Included among these alloys are wrought JESSOP* alloy JS-700, HAYNES** alloy 20 Mod, ALLEGHENY- LUDLUM*** alloy AL-6X and cast IN-862. Judging by their composition, their corrosion resistance in acetic acid and organic acids generally should be superior to Type 316 stainless steel in many halide contaminated environ- ments. Unfortunately, data on these alloys are sparse although some data exist as shown in Tables III, V, XIII, LXXII and LXXVIII. Note the superiority of alloy JS-700 in the acetic-hydroxy acid solution in Table V and the freedom from pitting exhibited by cast IN-862 in the buffered acetic acid solution at 200 C (392 F) shown in Table XIII. This type of alloy should certainly be evaluated for aggressive acetic acid environments. Welded samples of comparable thickness to the equipment under consideration are suggested for test evaluations because of the possible formation of sigma or chi phases.

Increases in temperature, increases in pressure and a more complex chemistry in the acetic acid process stream are characteristics of the more modern processes for produc- ing the acid. In many of these process streams, the presence of formic acid, higher acids, or halides requires that the ultimate material of construction in acid resis- tance, resistance to pitting and resistance to chloride stress- corrosion cracking be used. The nickel-base alloys containing molybdenum, iron and chromium are those materials. The alloys are exemplified by wrought HASTELLOY alloys C-276 and C-4, INCONEL* alloy 625, cast CHLORIMET** alloy 3 and ILLIUM*** alloys W1 and W2, among others. The data in Tables III, VII, VIII, XIII, XV1, XVII, XX, XXI, XXVII and XXVIII through XXX show the excel- lent resistance of these alloys to corrosion by hot acetic acids. In pure aqueous acid streams, or in uncontaminated glacial acids, the use of these alloys in preference to Type 316 stainless steel is usually not economically justifiable. However, when impurities are present, they often offer the most economical choice.

* Trademark of the Inco family of companies ** Trademark of The Duriron Company, Inc. *** Trademark of Stainless Foundry & Engineering, Inc.

* Trademark of Jessop Steel Company ** Trademark of Cabot Corporation ***Trademark of Allegheny Ludlum Steel Corporation

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