Nickel Insitute - Nickel Alloys in Organic Acids & Related Compounds

Nickel plating appears to have essentially the same corrosion resistance in acetic acid solutions as the wrought metal. An increase in corrosion resistance is reported for electroless nickel which is properly heat treated. Volokhova, et al. report rates of .10 and .05 mm/y (4 and 2 mpy) for untreated electroless nickel plate in 5% and glacial acid, respectively, at room temperature while specimens of heat-treated plating showed only .01 and nil mm/y (0.3 and 0.09 mpy) in the same acids. 20

tion. Such a situation demands more detailed testing and economic evaluation of alloys, taking into account not only first cost but maintenance costs and reliability as well. a. Oxidation of Acetaldehyde The oldest of the current processes used for any significant production of acetic acid is the oxidation of acetaldehyde. In this process, acetaldehyde is air-blown in a small tubular converter with distillation of the product and recycling of unreacted acetaldehyde to the reactor. 21 , 22 The primary converter product contains, in addition to acetic acid and unreacted acetaldehyde, varying quantities of acetic anhydride, ester, peracetic acid and catalyst salts from the converter. As pointed out previously, the pre- sence of the anhydride increases the corrosive nature of the stream. (See Tables IV, IX and X.) Until the anhydride and catalyst salts are separated from the acid, a close evaluation of the corrosion to be expected in all sections of the equipment is necessary. For instance, the still used to separate the acid and anhydride may require a nickel- base molybdenum-chromium-iron alloy for the base ket- tle, the calandria and a few lower sections of the column.

O. Process and Plant Corrosion Data 1. Acetic Acid Production

The modern industrial chemical plant has changed radi- cally during the past few decades. Efficient, economical production requires large single-train units that put greater emphasis on the reliability of components. If a failure does occur, it causes a shutdown of the entire process. When this happens, production losses will often far overshadow any differences in cost between alloys of marginal corro- sion resistance and more durable materials of construc-

TABLE XXVIII

Corrosion of Alloys in a Hydrocarbon Oxidation Unit for Acetic Acid

Corrosion Rate

Location *

1

2

3

4

5

6

7

8

9

Alloy

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

– –

– – 2 –

– –

– – 2

– –

– – 2 –

– –

– – 1 –

– –

– –

– –

– –

– –

– – 1 –

– –

– – 2 – – – – – – – – – – – – – – – – – – – – 3

28

11 12 <1

Type 304 Stainless Steel Type 202 Stainless Steel Type 316 Stainless Steel Type 317 Stainless Steel Type 329 Stainless Steel CARPENTER alloy 20Cb-3 HASTELLOY alloy G HASTELLOY alloy C HASTELLOY alloy B INCONEL alloy 600 IN alloy 102 MONEL alloy 400 STELLITE alloy No. 3** STELLITE alloy No. 4 STELLITE alloy No. 6 HAYNES alloy No. 93** HAYNES alloy 25 ILLIUM B*** ILLIUM P

.30

.05

.05

.05

.03

.25

10

.03

1

.03

.05

<.03

–

– – <.03 <1 <.03 < 1 – – <.03 < 1 – – – – – – – – – – – – – – – – – – – – – – – – – – .08 3 Nil Nil Nil Nil – –

–

– –

– –

– – 2

– –

– – – – – – – – – – – – – – – – – – – –

.03

1 – –

.05 2 <.03 <1 – – .10 4 – – .13 5 .05 2 – – – – – – – – – – – – – – – – – – – – – – <.03 <1 – – – –

.05 2 <.03 <1 – – .10 4 – – – – – – – – – – – – – – – – – – – – – – – – – – – – Nil Nil – – – –

– <.03 < 1 <.03 <1 .05 2 – – – – – – – – .10 4 .18 7 .46 18 >2.54 >100 .03 1 <.03 < 1 <.03 <1 <.03 <1 .10 4 – – – – – – – –

– <.03 <1 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – .05 2

– – <.03 <1 – – Nil Nil – – – – – – – – – – – – – – – – – – – – – – – – – – – – .69 27 – – .10 4

– – –

.05

– – <.03 < 1 – – – – – – <.03 <1 – – – – – – – – – – – – – – – – – – – – .56 22 – – – –

– <.03 < 1 5.59 220 – – – – 3.56 140 – – – – – – – – – – – –

Nil

Nil

– – – – – – –

ILLIUM PD ILLIUM 98 DURICHLOR**** Titanium Zirconium

– – – – –

Copper C70600

.08

(90-10Cupro-Nickel)

–

–

–

–

–

–

–

–

.05

2

.05

2

–

–

.10

4

–

–

* See process diagram Figure 4. ** Trademarks of Cabot Corporation *** Trademark or Stainless Foundry & Engineering, Inc. ****Trademark of The Duriron Company, Inc.

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