Nickel Insitute - Nickel Alloys in Organic Acids & Related Compounds

service in specific applications. It will be noted that some rates exceeding .25 mm/y (10 mpy) have been obtained for the Type 316 alloy in lactic acid at boiling temperatures. At the higher temperatures, it is considered to be good practice to use an L-grade stainless steel if welding is to be performed on the alloy. Table LXVI shows appreciable differences for annealed and sensitized conditions for cast stainless steels exposed to the acid at elevated tempera- tures and pressures. This admonition is true for the use of the stainless steels in all of the organic acids when exposed at the higher temperatures.

The use of Alloy 400 and the copper-nickel alloys is dependent on the aeration to be encountered in the acid stream. Nickel-copper alloy 400 has excellent resistance to all concentrations of the hot lactic acid solutions in the absence of air. However, corrosion becomes excessive if aeration is provided as a condition of the exposure.

TABLE LXVI

High Temperature Exposure of Cast Stainless Steels in Aqueous 50% Lactic Acid (Laboratory tests in autoclaves for 18-22 hours at temperatures shown)

Corrosion Rate

107 ºC (225 ºF)151 ºC (304 ºF)157 ºC (315 ºF)162 ºC (324 ºF)

Alloy

mm/y mpy

mm/y mpy

mm/y mpy

mm/y mpy

– – 44.20 1740 Nil Nil 2.03 80 – –

27.94 1100 39.88 1570 – – – – – –

– – –

– – –

CF-8 CF-8* CF-8M CF-8M* Copper

Nil Nil Nil Nil

Nil Nil Nil Nil 90

.99

39 65

1.65

2.29

*650 ºC (1202 ºF) for one hour, water quenched.

Reference 9

4200-Gallon Uniframe Transport Container. One of a fleet of five Uniframe Type 304 stainless steel transport tanks with 6  of foam in- place insulation being lifted aboard ship at Seattle with a load of milk for Alaska. These tanks make the long trip by flatbed truck trailer, ship, and rail flatcar between Seattle and Alaska.

TABLE LXVII

Corrosion of Alloys in Boiling Aqueous Lactic Acid Solutions During Five-Day Laboratory Tests

3. Tartaric Acid Tartaric acid (dihydroxybutanedioic acid) is one of the more innocuous acids produced in large quantity. As indicated by Table LXVIII, the product is not aggressive in aqueous solution up to the boiling point. Any of the austenitic stainless steels maintain purity in the product and prevent undesired contamination when storing or processing the tartaric acid solutions. Higher alloys are not indicated to be required for such service. 4. Citric Acid Citric acid (hydroxypropane tricarboxylic acid) is a more aggressive compound. This tart-tasting constituent of citrus products can be handled well by the austenitic stainless steels. Data for many of the other alloys are shown in Table LXIX. Here it will be noted that Alloy 400 is a candidate for use in many of the food product services. Others have described the use of MONEL alloy 400 and use. 14, 41, 42 other nickel-base alloys for such As with the other organic acids, the presence of air will determine the rate of corrosion on Alloy 400 in these solutions. Alloy 600 and other alloys of chromium and nickel have good resistance to the acid and can be used when desired.

Corrosion Rate

Alloy

mm/y

mpy

mm/y mpy mm/y mpy

.08–54.61 3–2150

56.64 2230

7.21 284

Type 304 Stainless Steel Type 309 Stainless Steel Type 316 Stainless Steel CARPENTER alloy 20Cb-3 INCOLOY alloy 825 HASTELLOY alloy C-276 HASTELLOY alloy B

3.30

130

–

–

–

–

<.03–.38 <1–15

.03

1

.08–.33 3–13

<.03

<1

.03

1

.18

7

<.03

<1

–

–

–

–

.05

2

.03

1

.03

1

–

–

.10

4

.05

2

INCONEL alloy 600 MONEL alloy 400 Copper Zirconium Titanium Tantalum Columbium

–

–

.43

17

.38

15

.13–.33

5–13

.15

6

.15

6

.33

13

.05

2

.08

3

Nil

Nil

Nil

Nil

Nil

Nil

.03

1

.03

1

<.03

<1

Nil

Nil

Nil

Nil

Nil

Nil

<.03

<1

–

–

<.03

<1

References 49, 51

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