Nickel Insitute - Nickel Alloys in Organic Acids & Related Compounds

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TABLE LVII

Corrosion of Alloys in Aqueous Maleic Acid Solutions

Corrosion Rate

2%*

5%*

10%*

30%**

40%*

59%**

Alloy

mm/y

mpy

mm/y

mpy

mm/y

mpy

mm/y

mpy

mm/y

mpy

mm/y

mpy

.03

4.06

160

4.06

160

3.71

146

5.33

210

Type 304 Stainless Steel Type 316 Stainless Steel

Nil

<.03

Nil

<.03

CARPENTER alloy 20 HASTELLOY alloy C HASTELLOY alloy B Nickel 200 Copper (C10200) Silver (fine)

–

<.03

–

<.03

–

<.03

–

.08

–

.91

–

.10

–

.03

–

Nil

*At 50 ºC (122 ºF) for 4 days with agitation by aeration. **Boiling for 6 days without aeration or deaeration.

Actually, there is little industry interest in maleic acid. The acid is a contaminant in processes used to produce maleic anhydride and phthalic anhydride. These anhydrides are important basic building blocks for the preparation of polyester and alkyd resins, plasticizers and agricultural chemicals. The isomer of maleic acid, termed fumaric acid, has commercial applications in the prepara-

tion of paper sizing and other resinous products as well as the synthesis of food additives. The presence of maleic acid in process streams of the anhydrides does create corrosion problems. The anhydrides are essentially innocuous, but the presence of malefic acid at the high temperatures used in the various processes means attack on lower alloys by streams con-

TABLE LVllI

Field Exposure of Alloys in a Phthalic Anhydride Plant

Corrosion Rate

Exposure a

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

1 2

2 2

– – –

.03 .05

.05 .05

– – –

–

Mild Steel Cast lron (gray) Ni-Resist Type IV

1.22 48 .56 22 .10 4 .03 1 .03 1 .03 1 – – – – – – – – – – – – .03 1 .08 3 .08 3 1.14 45 – – .03 1

.01* 0.4* .01 0.3 .01 0.2 Nil <0.1 Nil <0.1 Nil <0.1 – – – – – – – – – – – – Nil <0.1 Nil <0.1 Nil <0.1 .69 27 – – .05* 2

– – –

– –

– – –

– –

1.93 76 –

>7.62 >300 – – – – – – 2.21 87

3.10 122 3.02 119 .97 38 .28 11 – – .02 0.6 Nil <0.1 – – – – – – – – – – .15 6 .69 27 .13 5 .46 18 – – .56 22

– – –

– Nil –

– –

1 .03 <0. Nil 1 Nil <0. Nil 1 – <0. – 1 – – – – – – – – Nil – Nil – .05 <0. .18 1 – 0.1 Mel 0.2

1 .03 0.2 .01 0.4 .01 0.2 .01 <0. Nil 1 Nil <0. – 1 Nil – – <0. – 1 .01 – Nil – .01 0.4 .13 0.1 – 0.2 .02 5

39 .99 19 .48 0.3 .01 0.1 Nil <0. Nil 1 – – Nil <0. – 1 – – .84 – 1.88 33 1.12 74 – 44 – – – –

– .41 16 – – .02 0.6 – – – – – – – – – – – – – – – – – – – – – – – –

– 5.08 200 – – Nil 0.1 – – .02 0.7 Nil 0.1 – – – – – – – – – – – – – – – – – –

–

39 48

.99

– <0.1 Nil – – <0.1 –

Type 304 Stainless Steel Type 309 Stainless Steel Type 316 Stainless Steel Type311 Stainless Steel CARPENTER alloy 20 ACI CN-7M INCOLOY alloy 825 HASTELLOY alloy C HASTELLOY alloy B INCONEL alloy 600 Nickel 200 MONEL alloy 400 Copper Titanium Aluminum 3003

.56 22 – .01 3.3 –

.01 0.2 – – .01 0.2 Nil 0.1 Nil 0.1 – – .01 0.2 Nil Nil .01 0.3 Nil 0.1 .01 3 .01 2 – – – – – –

Nil 0.1 – – Nil <0.1 Nil <0.1 .01 0.2 – – Nil 0.1 – – – – 0.1 0.3 .18 7 .20 8 – – – – – –

1.22

–

.02 0.7 Nil 0.1 – – Nil <0. – 1 Nil – .02 0.1 .56 0.8

.99 39 .28 11 .86 34 – – .51 20 Nil <0.1 – –

– Nil –

– Nil Nil Nil Nil – – – – – – – – – – – – – – – – – –

– <0.1 01 – >5.0 0.2 8 >200 01 0.4 >5.0 >200 8 160 4.06 – – < 0.1 Nil –

1.22 48 – – 51 20 – – – – – –

22 51

1.55

.56

– – –

*Pitting

FIXED BED NAPHTHALENE OXIDATION UNIT a 1- Mixture of phthalic and malefic anhydride vapors near exit throat of a converter at 200-380ºC (329-716ºF) for 71 days. High temperature excursion to cause melting of 3003 aluminum. 2- Vapors of phthalic and maleic anhydride near bottom of distillation column at 204ºC (396ºF) for 16 days. 3- Same column as No. 2, but exposed at top at temperature of 195ºC (383ºF). 4- Liquid and vapor of phthalic anhydride in the lights heater at 177ºC (351ºF) for 157 days. 5- Overhead of distillation column for phthalic acid dehydration to phthalic anhydride and resulting distillation at 107-143ºC (225-289ºF) for 14 days. 6- Near top of batch still column with phthalic and malefic acids present. Distillation Involved 1 :10 ratio of total reflux versus distillation at 100-143ºC (212-289ºF) for 95 days. 7- On top tray of phthalic anhydride purification still with small amount of malefic acid and water present at 96-140ºC (205-284ºF) for 45 days. Vapor velocity of 7 ft per sec. 8- Top of distillation column for phthalic and maleic acids at 70ºC (158ºF) for 22 days. 9- Vapor space of column distilling 7% phthalic acid in water at 180ºC (356ºF) for 40 days. 10- Immersed in maleic acid recovery holding tank (10-18% maleic acid plus little phthalic acid and a-naphthoquinine) at 35ºC (95ºF) for 27 days. 11- Crude phthalic anhydride vapor in treater tank at 160-285ºC (320-545ºF) for 59 days. Liquid and vapor exposures essentially the same. 12- On reflux distributor plate of batch still handling crude phthalic anhydride containing phthalic acid, malefic acid, benzoic acid and maleic anhydride at 165-260ºC (329-500ºF) for 56 days. 13- Same as No. 12, but in another plant using temperatures of 225-290ºC (437-554ºF) for 85 days. 14- Same as No. 11, but in plant of No. 12. Essentially same temperatures for 25 days.

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