Nickel Insitute - Nickel Alloys in Organic Acids & Related Compounds

contaminate an acetic acid stream with halide ions, the use of the nickel-base, high alloy materials offers the greatest certainty of economical operation. As discussed under the effects of contaminants, the presence of chlorides in an acetic acid stream may produce disastrous results with the stainless steels. Titanium is also severely attacked when sufficient chloride ion is present. The copper alloys may be useful depending on the corrosion allowable in the system and depending on what other contaminants are in the stream (e.g., oxygen, heavy metal cations, peroxides, etc.). The nickel-base alloys containing molybdenum, chromium and iron are essentially unaffected by such contaminants. As an example, the data of Table XVII show the results of a test conducted in an acetic acid vaporizer using acid contaminated with a small amount of chloride. The effect on other alloys was severe while the HASTELLOY alloy C-276 material maintained adequate stability.

As shown previously, the presence of anhydride in the acetic acid can render the use of Type 316 stainless steel unsuitable. Titanium is also attacked by the acid- anhydride mixtures (Table XXI). These nickel-base higher alloys retain immunity to attack in all mixtures of the acid and anhydride. For this reason, parts of the distillation columns of the acetaldehyde-to-acetic acid process were constructed of these high alloy wrought materials and many of the required pumps were of the cast counterparts. When formic acid is a co-product of the oxidation reaction to produce acetic acid, the process stream can again be overly aggressive to Type 316 stainless steel and more highly alloyed corrosion resistant alloys must be considered for use. If air or other contaminants are present, the nickel-base molybdenum-chromium-iron al- loys are prime candidates as materials of construction. When the process conditions or operating problems

TABLE XXI

Comparison of Corrosion of Various Proprietary Alloys in Acetic Acid Solutions

Conditions: Duplicate specimens tested in the boiling solution for 48 hours or longer. Air not excluded or added.

Corrosion Rate

50% Acetic Acid 50% Acetic Anhydride

10% Acetic Acid 2% Formic Acid

99% Acetic Acid 1% Acetic Anhydride

90% Acetic Acid 10% Formic Acid

90% Acetic Acid 10% Acetic Anhydride

Acetic Acid, glacial

30% Aqueous Acetic Acid

Esterifi- cation Mixture 1

Acetic Acid 70%

mm/y mpy mm/y mpy

mm/y mpy mm/y mpy mm/y mpy

mm/y mpy mm/y mpy

mm/y mpy

mm/y mpy

Alloy

.01 0.4

1.07

42

.03

1

<.03 < 1

9.12

359

.23

9

.17

6.5

–

–

–

–

Type 316 Stainless Steel INCOLOY alloy 825 IN alloy 102 (A) 2 IN alloy 102 (HT) 3 INCONEL alloy 625 (A) 2 INCONEL alloy 625 (HT) 3 HASTELLOY alloy D WAUKESHA * No. 23 WAUKESHA No. 54 WAUKESHA No. 88 KROMARC ** 55 JESSOP JS-700 CARPENTER alloy 20 4 Multiphase MP35N *** CROLOY ***** 16-1 Chromium Carbide with 12% nickel binder HASTELLOY alloy C-276 Titanium

1.70 67 <.03 < 1 .03 1.1 <.03 < 1

20.24 797 .69 27 .71 28 .08 3

– – – –

– – – –

.36 .15 .10 .03

14

3.66

144

– – – –

– – – –

– – – –

– – – –

– – – –

– – – –

– – – –

– – – –

6 4 1

.18 .18 .28

7 7

11

<.03 < 1

.08

3

–

–

.03

1

.28

11

–

–

–

–

–

–

–

–

<.03 < 1

.38

15

–

–

.04

1.5

.28

11

–

–

–

–

–

–

–

–

<.03 < 1 <.03 < 1 .76 30 .64 25 1.12 44 .18 7 – – – – .05 2

1.83

72

– – – – – – – – –

– – – – – – – – –

– – – – – – – – –

– – – – – – – – –

6.12

241

<.03 < 1 – – – – – – – – .41 1 6 – – – – – –

<.03 < 1 – – .15 6 .76 30 .28 11 .08 3 – – – – – –

–

– 2 – – – – – – –

– –

– –

–

–

–

–

.05

.69

27 47 36 97

.71

28 45

– – – – – – –

1.45

57 24 22

1.19

1.14

.61 .56

.91

.05

2

2.46

4.09

161

– – – –

– – – –

.03 .03

1

.66 .36

26 14

1 <.03 < 1

–

–

1.47 58 – –

.43 .69

17 27

5.84 230 – –

– –

– –

10.67 420 1.50 59

– –

– –

– –

– –

– –

– –

– –

– –

1. Synthetic mixture of 75% butyl acetate, 11% butanol, 10% acetic acid, 4% water, 0.3% sulfuric acid 2. Annealed 3. 840 ºC (1544 ºF) for one-half hour and furnace cooled 4. CARPENTER alloy 20 has been superseded by an improved alloy CARPENTER alloy 20Cb-3

* Trademark of Waukesha Foundry Company ** Trademark of Westinghouse Electric Corporation *** Trademark of Standard Pressed Steel Co. ***** Trademark of Babcock & Wilcox Co.

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