Alloy 20

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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.

Inventory

Product form	Size range from	Size range to
Alloy 20 sheet & plate	1.6 mm	76.2 mm	GET A QUOTE
Alloy 20 round bar	10 mm	279.4 mm	GET A QUOTE
Alloy 20 pipe	0.5 in	10 in	GET A QUOTE
Alloy 20 pipe fittings	0.5 in	10 in	GET A QUOTE
Alloy 20 flanges	0.5 in	10 in	GET A QUOTE

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Flanges

Pipe Fittings

Pipe

Sheet & Plate

Round Bar

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Chemical Analysis

%	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

Applications

Perfect for applications in the Chemical Processing Industry

Alloy 20 can be used in a variety of applications, here are just a few examples:

Sulfuric acid pickling tanks, racks and heating coils
Phosphate coating drums and racks
Heat exchangers
Process piping
Tanks
Pumps and valves
Gaskets
Mechanical seals
Process equipment for manufacture of bullet-proof fibre, Kevlar

About Alloy 20

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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Properties

Density:: 7.695 g/cm³ annealed
Melting range:: 1385-1443°C
Electrical resistivity:: 1.08 x 10^-6 Ω⋅m
Poisson's Ratio:: 0.31

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Mechanical & Physical Properties
Aqueos Corrosion Data

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	Sulfuric Acid	70 (21)	2
5% H²SO⁴	Sulfuric Acid	140 (60)	10
5% H²SO⁴ w/Air	Sulfuric Acid	86 (30)	61
19% H²SO⁴	Sulfuric Acid	223 (106)	110
20% H²SO⁴	Sulfuric Acid	70 (21)	4
50% H²SO⁴ w/Air	Sulfuric Acid	86 (30)	16
5% H²SO⁴	Sulfuric Acid	255 (124)	1000
93% H²SO⁴ w/Air	Sulfuric Acid	86 (30)	10

Mechanical & Physical Properties

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

Aqueos Corrosion Data

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	Sulfuric Acid	70 (21)	2
5% H²SO⁴	Sulfuric Acid	140 (60)	10
5% H²SO⁴ w/Air	Sulfuric Acid	86 (30)	61
19% H²SO⁴	Sulfuric Acid	223 (106)	110
20% H²SO⁴	Sulfuric Acid	70 (21)	4
50% H²SO⁴ w/Air	Sulfuric Acid	86 (30)	16
5% H²SO⁴	Sulfuric Acid	255 (124)	1000
93% H²SO⁴ w/Air	Sulfuric Acid	86 (30)	10

Specifications

UNS Number:: N08020
W.Nr.Number:: 2.4660
ASTM Standards:: A240, B366, B462, B463, B464, B468, B472, B473, B474, B475, B729, B775
ASME Standards:: SB463, SB464

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FAQs & Resources

What is chloride induced stress corrosion cracking?

Stress corrosion cracking (SCC) is the growth of a crack formation in a corrosive environment. It can lead to unexpected sudden failure of normally ductile metals subjected to a tensile stress, especially at an elevated temperature.

Chloride induced stress corrosion cracking is one of the most common reasons why austenitic stainless steel pipework and vessels deteriorate in the chemical processing and petrochemical industries. Deterioration By Chloride induced stress corrosion cracking can lead to failures that have the potential to release stored energy and/or hazardous substances.

At 33% Nickel content alloy 20 is virtually immune to Chloride induced stress corrosion cracking.

What are the main types of corrosion?

Uniform corrosion, localised corrosion pitting & crevice corrosion, intergranular corrosion and galvanic corrosion.
Alloy 20 is resistant to intergranular corrosion in the as welded condition.

What is intergranular corrosion?

Intergranular corrosion (IGC), also known as intergranular attack (IGA), is a form of corrosion where the boundaries of crystallites of the material are more susceptible to corrosion. This is created by the formation of intermetallic carbides at the grain boundaries resulting in the formation of Chromium-depleted zones adjacent to the grain boundaries. Often referred to as sensitisation of the material.

What are the key benefits of alloy 20?

This alloy was developed specifically for hot sulphuric acid applications. It also demonstrates excellent general corrosion resistance. Niobium stabilisation allows the material to be used in corrosion environments in the as welded condition.

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