Alloy SSC-6MO (UNS N08367) – High-Performance Super-Austenitic Stainless Steel

Mechanical Properties

Typical Room Temperature Mechanical Properties, Mill Annealed
Properties Applicable to Plate

Yield Strength 0.2% Offset		Ultimate Tensile Strength		Elongation in 2 in. (50mm)	Reduction percent of area	Hardness Rockwell B
psi (min.)	(MPa)	psi (min.)	(MPa)
55,000	380	107,000	738	48	60	90

Corrosion Properties

The most frequent cause of corrosion failures in stainless steels is localized attack induced by chlorides; specifically, pitting, crevice corrosion and stress-corrosion cracking. SSC-6MO is positioned as an upgrade to austenitic stainless grades such as 316L, 317L and 904L. It is also superior to Alloy 20 and Alloy 825 in resistance to a wide range of corrosive environments. SSC-6MO is also found to be a cost effective substitute for higher cost nickel-base alloys such as alloys G, 625, 276 and titanium for many applications.

Chloride Pitting Resistance

The pitting resistance of an austenitic stainless steel can be related directly to alloy composition, where chromium, molybdenum and nitrogen are a weight %. The Pitting Resistance Equivalent Number (PREN) uses the following formula to measure an alloy’s relative pitting resistance – the higher the number, the better the pitting resistance.

PREN = %Cr + 3.3Mo + 30N

The PREN values for several alloys are presented in the following chart:

Composition

Crevice Corrosion Resistance

The high level of molybdenum and nitrogen present in SSC-6MO has a beneficial effect on crevice corrosion resistance in chloride-bearing, oxidizing, acid solutions. SSC-6MO also has better crevice corrosion resistance in seawater than 316L, 2205 and 904L.

The Critical Crevice Corrosion Temperature (CCCT) test is often used to compare the crevice corrosion resistance of various alloys.

Temperature for the Initiation of Crevice Corrosion in a 10% Ferric Chloride Solution

Alloy	Critical Crevice Corrosion Temp, °F	Temp, °C
316L	27	-2
Alloy 825	27	-2
317L	35	2
317LMN	68	20
2205	68	20
904L	68	20
Alloy G	86	30
SSC-6Mo	95	35

Stress-Corrosion Cracking Resistance

Chloride stress-corrosion cracking (SCC) is one of the most serious forms of localized corrosion. Higher temperatures and reduced pH will increase the probability of SCC. It has been determined that alloys become more resistant to SCC as their nickel content increases above 12% and their molybdenum content rises above 3%. SSC-6MO is superior to the standard 300 series austenitic stainless steels and some duplex stainless steels. SSC-6MO is very resistant to SCC at temperatures less than 250°F (121°C). The threshold temperature for initiating SCC increases with decreasing chloride content. Caution must be used when selecting this alloy for applications where temperatures may be higher than 250°F (121°C).

General Corrosion

Chloride stress-corrosion cracking (SCC) is one of the most serious forms of localized corrosion. Higher temperatures and reduced pH will increase the probability of SCC. It has been determined that alloys become more resistant to SCC as their nickel content increases above 12% and their molybdenum content rises above 3%. SSC-6MO is superior to the standard 300 series austenitic stainless steels and some duplex stainless steels. SSC-6MO is very resistant to SCC at temperatures less than 250°F (121°C). The threshold temperature for initiating SCC increases with decreasing chloride content. Caution must be used when SSC-6MO is excellent in acetic, formic and phosphoric acids, as well as, sodium bisulfate. It is satisfactory in oxalic acid, sodium hydroxide and sullfamic acids but unsatisfactory in 10% sulfuric acid solutions. The overall general corrosion resistance of SSC-6MO in boiling test solutions is superior to 316L and 317L, and comparable to 904L and 276.

The resistance of SSC-6MO to dilute (less than 15%) sulfuric acid at all temperatures up to the boiling point and to concentrated (greater than 85%) solutions at low temperatures is good for an austenitic stainless steel. In pure sulfuric acid, SSC-6MO performs significantly better than 316L and somewhat better than 904L. Its performance is comparable to the more costly nickel-base materials – Alloy 20 and Alloy 825.

In phosphoric acid process streams that contain halide impurities, the superior resistance of SSC-6MO is required. The alloy also resists concentrations above 45% where Alloy 20 and Alloy 825 are usually utilized.

AL6XN® is a registered trademark of ATI Properties Inc. Selecting this alloy for applications where temperatures may be higher than 250°F (121°C).

NOTE: The information and data in this product data sheet are accurate to the best of our knowledge and belief, but are intended for informational purposes only, and may be revised at any time without notice. Applications suggested for the materials are described only to help readers make their own evaluations and decisions, and are neither guarantees nor to be construed as express or implied warranties of suitability for these or other applications. Stainless Steel, Nickel Alloy and Titanium products are classified as sheet if the thickness of the metals is less than 3/16” (4.7mm). If the thickness of the metal is 3/16” (4.7mm) or more, then it is considered a plate.

Mechanical Properties

Typical Room Temperature Mechanical Properies, Mill Annealed
Properties Applicable to Plate

Yield Strength 0.2% Offset		Ultimate Tensile Strength		Elongation in 2 in. (50mm)	Reduction percent of area	Hardness Rockwell B
psi (min.)	(MPa)	psi (min.)	(MPa)
55,000	380	107,000	738	48	60	90

Corrosion Properties

The most frequent cause of corrosion failures in stainless steels is localized attack induced by chlorides; specifically, pitting, crevice corrosion and stress-corrosion cracking. SSC-6MO is positioned as an upgrade to austenitic stainless grades such as 316L, 317L and 904L. It is also superior to Alloy 20 and Alloy 825 in resistance to a wide range of corrosive environments. SSC-6MO is also found to be a cost effective substitute for higher cost nickel-base alloys such as alloys G, 625, 276 and titanium for many applications.

Chloride Pitting Resistance

The pitting resistance of an austenitic stainless steel can be related directly to alloy composition, where chromium, molybdenum and nitrogen are a weight %. The Pitting Resistance Equivalent Number (PREN) uses the following formula to measure an alloy’s relative pitting resistance – the higher the number, the better the pitting resistance.

PREN = %Cr + 3.3Mo + 30N

The PREN values for several alloys are presented in the following chart:

Composition

Crevice Corrosion Resistance

The high level of molybdenum and nitrogen present in SSC-6MO has a beneficial effect on crevice corrosion resistance in chloride-bearing, oxidizing, acid solutions. SSC-6MO also has better crevice corrosion resistance in seawater than 316L, 2205 and 904L.

The Critical Crevice Corrosion Temperature (CCCT) test is often used to compare the crevice corrosion resistance of various alloys.

Temperature for the Initiation of Crevice Corrosion in a 10% Ferric Chloride Solution

Alloy	Critical Crevice Corrosion Temp, °F	Temp, °C
316L	27	-2
Alloy 825	27	-2
317L	35	2
317LMN	68	20
2205	68	20
904L	68	20
Alloy G	86	30
SSC-6Mo	95	35

Stress-Corrosion Cracking Resistance

Chloride stress-corrosion cracking (SCC) is one of the most serious forms of localized corrosion. Higher temperatures and reduced pH will increase the probability of SCC. It has been determined that alloys become more resistant to SCC as their nickel content increases above 12% and their molybdenum content rises above 3%. SSC-6MO is superior to the standard 300 series austenitic stainless steels and some duplex stainless steels. SSC-6MO is very resistant to SCC at temperatures less than 250°F (121°C). The threshold temperature for initiating SCC increases with decreasing chloride content. Caution must be used when selecting this alloy for applications where temperatures may be higher than 250°F (121°C).

General Corrosion

Chloride stress-corrosion cracking (SCC) is one of the most serious forms of localized corrosion. Higher temperatures and reduced pH will increase the probability of SCC. It has been determined that alloys become more resistant to SCC as their nickel content increases above 12% and their molybdenum content rises above 3%. SSC-6MO is superior to the standard 300 series austenitic stainless steels and some duplex stainless steels. SSC-6MO is very resistant to SCC at temperatures less than 250°F (121°C). The threshold temperature for initiating SCC increases with decreasing chloride content. Caution must be used when SSC-6MO is excellent in acetic, formic and phosphoric acids, as well as, sodium bisulfate. It is satisfactory in oxalic acid, sodium hydroxide and sullfamic acids but unsatisfactory in 10% sulfuric acid solutions. The overall general corrosion resistance of SSC-6MO in boiling test solutions is superior to 316L and 317L, and comparable to 904L and 276.

The resistance of SSC-6MO to dilute (less than 15%) sulfuric acid at all temperatures up to the boiling point and to concentrated (greater than 85%) solutions at low temperatures is good for an austenitic stainless steel. In pure sulfuric acid, SSC-6MO performs significantly better than 316L and somewhat better than 904L. Its performance is comparable to the more costly nickel-base materials – Alloy 20 and Alloy 825.

In phosphoric acid process streams that contain halide impurities, the superior resistance of SSC-6MO is required. The alloy also resists concentrations above 45% where Alloy 20 and Alloy 825 are usually utilized.

Alloy SSC-6MO Stainless Steel – Frequently Asked Questions

1. What is Alloy SSC-6MO stainless steel?

Alloy SSC-6MO (UNS N08367) is a super-austenitic stainless steel containing approximately 6% molybdenum, 24% nickel, and 21% chromium. It is designed for excellent resistance to chloride-induced corrosion, including pitting, crevice corrosion, and stress-corrosion cracking. It directly competes with AL6XN® and is often used as a cost-effective alternative to higher-cost nickel-base alloys.

2. What are common applications for SSC-6MO stainless steel plate?

SSC-6MO is widely used in highly corrosive environments, including:
• Seawater filtration and desalination systems
• Chemical and pharmaceutical processing equipment
• Heat exchangers, condensers, and piping in power generation
• Food and beverage process systems
• Offshore oil and gas production platforms
• Pulp and paper chlorine dioxide bleaching systems

3. How does SSC-6MO perform in chloride environments?

SSC-6MO demonstrates superior resistance to chloride pitting, crevice corrosion, and stress-corrosion cracking compared to 316L, 317L, and 904L. Its PREN value is significantly higher due to its elevated molybdenum and nitrogen content, offering excellent localized corrosion resistance in saltwater and brine applications.

4. What is the corrosion resistance of SSC-6MO compared to other stainless steels?

SSC-6MO outperforms 316L, 317L, 904L, and Alloy 20 in general corrosion resistance and is competitive with Alloy 625, Alloy G, and Alloy 276 in many environments. It is highly effective in halide-containing acid process streams and performs well in phosphoric and sulfuric acid service.

5. What are the mechanical properties of SSC-6MO stainless steel?

Typical mill-annealed values:
• Yield Strength (0.2% offset): 55,000 psi (380 MPa)
• Ultimate Tensile Strength: 107,000 psi (738 MPa)
• Elongation in 2″: 48%
• Reduction in Area: 60%
• Hardness: 90 Rockwell B

6. What are the physical properties of SSC-6MO?

• Density: 0.290 lbs/in³ (8.02 g/cm³)
• Modulus of Elasticity: 28.3 psi × 10.6 (75°F) (195 GPa)
• Thermal Conductivity at 212°F: 6.8 BTU-ft/hr-ft2/°F (68-212°F)
• Specific Heat: 0.11 BTU/lb-°F
• Electrical Resistivity: 535 Ohm-circ mil/ft
• Linear Coefficient of Expansion (68–212°F 8.9 10-6/°F
• Melting Range: 2470–2560°F (1354–1404°C)

7. Is SSC-6MO magnetic?

No. SSC-6MO is non-magnetic, even after cold working or welding.

8. Can SSC-6MO be welded and fabricated?

Yes. SSC-6MO has excellent weldability and formability. It is easier to fabricate than super duplex or high-alloy ferritic stainless steels, making it suitable for complex systems requiring high corrosion resistance and ease of processing.

9. What standards apply to Alloy SSC-6MO stainless steel?

• ASTM A240, B688
• ASME SA240, SB688

10. What thicknesses of SSC-6MO plate does Sandmeyer Steel stock?

Sandmeyer Steel stocks SSC-6MO stainless steel plate in thicknesses ranging from 3/16″ (4.8 mm) through 2″ (50.8 mm).

AL6XN® is a registered trademark of ATI Properties Inc. Selecting this alloy for applications where temperatures may be higher than 250°F (121°C).

Contact a Sandmeyer Steel Company Expert

NOTE: The information and data in this product data sheet are accurate to the best of our knowledge and belief, but are intended for informational purposes only, and may be revised at any time without notice. Applications suggested for the materials are described only to help readers make their own evaluations and decisions, and are neither guarantees nor to be construed as express or implied warranties of suitability for these or other applications. Stainless Steel, Nickel Alloy and Titanium products are classified as sheet if the thickness of the metals is less than 3/16” (4.7mm). If the thickness of the metal is 3/16” (4.7mm) or more, then it is considered a plate.