A nickel-iron-chromium grade, Alloy 20 is ideal for a wide range of corrosive environments.
With the addition of copper, molybdenum and niobium, Alloy 20 is the alloy of choice for sulphuric acid applications.
| % | Ni | Cr | Mo | Mn | Cu | Si | C | S | P | Nb+Ta | Fe |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | 32.5 | 19 | 2 | - | 3 | - | - | - | - | 8.0 x C 1.0 | - |
| Max | 35 | 21 | 3 | 2 | 4 | 1 | 0.06 | 0.035 | 0.035 | - | Balance |
Alloy 20 contains niobium for stabilisation which enhances its corrosion resistance. The alloy is an iron-base, austenitic alloy with excellent corrosion resistance to a wide range of media.
With the high nickel content, Alloy 20 shows good resistance to chloride-induced stress corrosion cracking. In addition the alloy also has good resistance to pitting and crevice corrosion.
In the chemical process market, key applications of Alloy 20 are in sulphuric, phosphoric and nitric acid environments.
The alloy is also commonly used in the food industry for the manufacture of food preservatives (phosphorus oxychloride and phosphorus trichloride).
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| Mechanical & Physical Properties | 21.1°C | 49.4°C | 100°C | 150°C | 200°C | 300°C | 350°C | 400°C | 450°C | 500°C | 900°C |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Ultimate Tensile Strength /MPa | 551.6 | - | - | - | - | - | - | - | - | - | - |
| 0.2% Yield Strength /MPa | 241.3 | - | - | - | - | - | - | - | - | - | - |
| Reduction of area % (for bar) | 50 | - | - | - | - | - | - | - | - | - | - |
| Elongation % | 30 | - | - | - | - | - | - | - | - | - | - |
| Coefficient of Thermal Expansion µm/m⁰C | - | - | 14.7 | 14.9 | 15.1 | 15.5 | 15.7 | 15.9 | 16 | 17.2 | |
| Thermal Conductivity /kcal/(hr.m.°C) | - | 125.9 | 135.1 | 153.3 | 169.6 | 187.5 |
| Media | Common Name | Temp °F (°C) | Corrosion Rate (mpy) |
|---|---|---|---|
| 5% CH³CO²H w/Air | Acetic Acid | 70 (21) | 40 |
| 10% CH³CO²H | Acetic Acid | 86 (30) | 3.4 |
| 56% CH³CO²H | Acetic Acid | 176 (80) | 66 |
| 85% CH³CO²H w/Air | Acetic Acid | 70 (21) | 400 |
| 98% CH³CO²H | Acetic Acid | 241 (116) | 12 |
| 50% NaOH | Caustic Soda | 195 (90) | 0.55 |
| 50% NaOH | Caustic Soda | 310 (155) | 0.5 |
| 75% NaOH | Caustic Soda | 250 (120) | 1.0 |
| 90% CH²O² | Formic Acid (Liquid) | 70 (21) | 4 |
| 90% CH²O² | Formic Acid (vapour) | 70 (21) | 7 |
| 1% HCL | Hydrochloric Acid | 214 (101) | 680 |
| 10% HCL | Hydrochloric Acid | 86 (30) | 80 |
| 10% HCL | Hydrochloric Acid | 221 (105) | 8000 |
| 10% HNO3 | Nitric Acid | 216 (102) | 12000 |
| 10% H3PO4 | Phosphoric Acid | 75 (24) | 0.6 |
| 10% H3PO4 | Phosphoric Acid | 214 (101) | 154 |
| 40% H3PO4 | Phosphoric Acid | 75 (24) | 1 |
| 500ppm NaClO | Sodium Hypochlorite | 77 (25) | 0.8 |
| 2% H2SO4 | Sulphuric Acid | 70 (21) | 2 |
| 5% H2SO4 | Sulphuric Acid | 140 (60) | 10 |
| 5% H2SO4 w/Air | Sulphuric Acid | 86 (30) | 61 |
| 19% H2SO4 | Sulphuric Acid | 223 (106) | 110 |
| 20% H2SO4 | Sulphuric Acid | 70 (21) | 4 |
| 50% H2SO4 w/Air | Sulphuric Acid | 86 (30) | 16 |
| 5% H2SO4 | Sulphuric Acid | 255 (124) | 1000 |
| 93% H2SO4 w/Air | Sulphuric Acid | 86 (30) | 10 |
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