Engineered stainless: 2x stronger yield than 316 stainless steel

Duplex Fastener Overview

Duplex 2205 and Super Duplex 2507 (UNS S32205 / UNS S32750) stainless steel fasteners are characterized by their high yield strength, which is twice that of annealed austenitic stainless steels, like 304 and 316. In addition, Duplex steels offer improved corrosion protection compared to 300 series stainless, especially in terms of localized corrosion such as crevice and pitting, as well as stress corrosion cracking.  In general, Duplex steel bolts are a great step up from 300 series stainless.

The main difference between the Duplex alloys is that 2507 offers higher strength and better corrosion resistance compared to Duplex 2205.
•  Duplex 2205 (1.4462): Higher strength and corrosion resistance than 300 series stainless.
•  Super Duplex 2507 (1.4410): Improved corrosion resistance and strength compared to 2205.

Mechanical Properties
Duplex 2205 bolts provide a typical UTS of 110ksi and a yield strength of 80ksi, whereas Super Duplex bolts offer slightly higher strength at 125ksi UTS and 82ksi yield. In general, Duplex fasteners have significantly better toughness and ductility than ferritic grades of steel, but not the levels of austenitic grades. Usage of both a Duplex screw and Super Duplex stainless steel screw should be limited to temperatures below 570°F, as extended exposure to elevated temperatures can embrittle this material.
Key properties:
•  High strength and fatigue resistance
•  Good toughness & ductility
•  Temperature usage limit: 570°F
•  Low thermal expansion

Corrosion Resistance
Though Duplex steel screws are not ideal for harsh chemical environments, they do offer better corrosion resistance than 300 series stainless steel and are ideal for saltwater and chloride applications. Duplex bolts offer resistance to:
•  Saltwater: salt air, brackish water and marine environments.
•  Localized chloride corrosion: pitting and crevice corrosion as well as stress corrosion cracking.
•  Sulfide stress corrosion resistance
•  Oxidation

Which Duplex Steel is Best for Your Application?
The most common grades of Duplex steel fasteners are Duplex 2205 and Super Duplex 2507. If you are still not sure, our engineering team is here to offer their expertise on which grade will meet the specific requirements of your application. We also offer other resources including Duplex Torque Specs.

Duplex Steel Fastener Stock and Availability

Common sizes of Duplex fasteners (both metric and standard) are kept in stock in both 2205 and 2507, including hex head bolts, hex nuts, lock washers and flat washers. Additionally any size could be made to order.

Custom Availability
We can make both common and custom-to-print Duplex fasteners. Typically, we require a minimum quantity of approximately 25 pieces, depending on the fastener size and type. We also can provide fasteners in Zeron 100, F55 and other grades. The lead time for Duplex fasteners is about 4 weeks. Be sure to contact us for specific lead times and expediting needs.
•  Diameter sizes:  Standard #00 – 4” in diameter / Metric M1.2 – M48
•  Threads: UNC, UNF, UNJ, UNR, Rolled or Cut
•  Minimum Volume – Typically 25pcs depending on size and stock
•  All ANSI/ASME and DIN / ISO standards
•  NACE MR0175, ASTM, ASME, MIL specifications, DFAR and Domestic available

Expediting Options
Let us know if you have lead time requirements that require a rush order so that we can accommodate them.

Duplex Fastener Styles

Duplex Screws 12 Point ScrewsButton Head Cap ScrewsFlat Head ScrewsHex Head Cap Screws, Pan Head Screws, Security Screws, Self Drilling Screws, Set ScrewsSocket Head Cap Screws, Vented Screws
•  DIN 603 / ISO 8677
•  DIN 912 / ISO 4762
•  DIN 913 / ISO 4026
•  DIN 914 / ISO 4027
•  DIN 915 / ISO 4028
•  DIN 916 / ISO 4029
•  DIN 921
•  DIN 931 / ISO 4014
•  DIN 933 / ISO 4017
•  DIN 961 / ISO 8676
•  DIN 965 / ISO 7046
•  DIN 966 / ISO 7047
•  DIN 7991 / ISO 10642
•  DIN 7380 / ISO 7380
•  DIN 84 / ISO 1207
•  DIN 85 / ISO 1580
•  DIN 34822
•  DIN 34821
•  DIN 7504 / ISO 15480
•  DIN 7984 
•  DIN 963 / ISO 2009
Duplex Bolts Hex Head Bolts, Shoulder Bolts, Wedge Anchor Bolts •  DIN 931
•  DIN 933
•  ISO 4014
•  ISO 4017
•  ISO 7370
Duplex Nuts Hex Nuts, Lock Nuts •  DIN 439 / ISO 4035
•  DIN 934 / ISO 4032
•  DIN 985 / ISO 7040
•  DIN 986
•  DIN 980 / ISO 7042 / ISO 19513
•  DIN 6923 / ISO 4161
Duplex Studs/Rod Studs, Threaded Rod, Weld Studs •  DIN 975
•  DIN 976
Duplex Washers Flat Washers, Lock Washer

•  DIN 125 / ISO 7089 / ISO 7090
•  DIN 126 / ISO 7091
•  DIN 127 / ISO 7090
•  DIN 9021 / ISO 7093

Common Duplex Bolt Grades

Duplex Alloy 2205 (1.4462)
Duplex 2205, UNS S32205, is a stainless steel material, whose “Duplex” name is derived from the mixed microstructure which contains roughly equal portions of ferrite and austenite. This grade is the most popular variety and this two-phase material is a significant upgrade from 316 stainless steel in terms of both yield strength and corrosion resistance. Click here for more in-depth information on a Duplex 2205 Screw.

DUPLEX 2205 SPECIFICATIONS: ASME SA 182, ASME SA 240, ASME SA 479, ASME SA 789, ASME SA 789 Section IV Code Case 2603, ASTM A 240, ASTM A 276 Condition A, ASTM A 276 Condition S, ASTM A 479, ASTM A 790, NACE MR0175/ISO 15156, NORSOK MDS D45 Grade F51, UNS S31803, UNS S32205, W. NR./EN 1.4462, Werkstoff 1.4462 Duplex

Duplex 2205 Chemistry

Super Duplex Alloy 2507 (1.4410)
Super Duplex 2507, UNS S32750, is a two-phase stainless steel and is particularly well suited for use in environments such as warm chlorinated seawater and acidic, chloride containing media. It has similiar properties to Duplex 2205 but is more corrosion resistant and performs well in moderately corrosive environments. Click here for more in-depth information on a Super Duplex 2507 Screw.

SUPER DUPLEX 2507 SPECIFICATIONS:  EN 10216-5, ASTM A789; A790, ASTM A182 ASTM A182, ASTM A815, ASTM A240, EN 10088-2, ASTM A479, EN 10088-3 EN 10088, ISO 15156-3, NACE MR0175, Werkstoff 1.4410 S.Duplex

Super Duplex 2507

Zeron 100 / F55
Zeron 100 fasteners are made of a high-grade Super Duplex steel alloy that is designed for more aggressive corrosion than grades 2205 and 2507.  Zeron 100 (also known as F55) has added copper and tungsten (compared to grade 2507) for improved corrosion resistance.  Zeron 100 bolts offer mechanical strength similar to Duplex 2205 with tensile strength of 109ksi and yield strength of 80ksi. Zeron 100 fasteners have a maximum usable temperature of about 572˚F. Click here for additional data on Zeron 100 bolt's performance in sulfuric acid.
Key Attributes  
•    High level of resistance to pitting and crevice corrosion in warm seawater
•    Excellent chloride-induced stress corrosion cracking and sulfide-stress cracking in sour-gas conditions
•    Better resistance to alkalis and acids than other Duplex grades
•    Improved resistance to fatigue and erosion corrosion that any other stainless steel alloy
•    Marine and desalination rely on Zeron 100 bolts for their high level of seawater corrosion resistance.
•    Zeron 100 is used in oil & gas, as well as flue gas desulfurization to protect from sulphide-stress cracking.
•    For resistance to chlorides, Zeron 100 fasteners are used in pulp & paper bleaching processes.

ZERON 100/F55 SPECIFICATIONS: ASTM A 182, ASTM A 182 (Grade F55), ASTM A 240, ASTM A 276, ASTM A 473, ASTM A 479, ASTM A 790, ASTM A 815, ASTM A314, NORSOK MDS 055, UNS S32760, W. Nr./EN 1.4501, Werkstoff 1.4501

Zeron 100 Chemistry


Duplex and Super Duplex Frequently Asked Question of the Week

Is a Coating Needed for Duplex Bolts in Saltwater?
Q: We would like to purchase Duplex parts. Can you xylan coat and Zinc nickel Electroplate them since they will be used in sea water?
A: It is not practical to coat a Duplex 2507 bolt as it is stainless steel and will not corrode in seawater. Duplex will provide great resistance to saltwater, salt air, chloride corrosion, oxidation, and stress corrosion caused by sulphides. These coatings are usually best applied to carbon steel that will corrode rapidly in air and water.

ASTM A1082 Bolting Specification

For special applications, Extreme Bolt & Fastener can also provide Duplex stainless steel fasteners per ASTM A1082 specification. This specification applies to bolting and has been approved for use by agencies of the Department of Defense. ASTM A1082 sets standards for chemical composition and mechanical properties. 

Mechanical Data

Duplex Stainless Tensile Data

Zeron 100 Iso Corrosion Chart 2

Duplex Steel Screws

12 Point    12 Point Screws Duplex and Super Duplex 12-point screws are ideal when higher torque (than a socket head or hex head) is needed. Duplex 12 point screws are typically less economical due to the intricacy to manufacture the head. Available in 1/4" or larger sizes. •  IFI-115
•  DIN 34822
•  DIN 34821
Button Head    Button Head Cap Screws Duplex steel button head screws provide a broad clamping area combined with a low-profile head. Button heads are most commonly available with a socket driver and are best for fastening materials that are too thin to counter bore. • ASME B18.3
• ASME 18.3.4M
• DIN 7380 / ISO 7380
Flat Head 3D    Flat Head Screws Typically offered in an 82° countersink angle, Duplex flat heads can also be custom made to other angles from 60° -120°. These screws are designed to be flush with the surface. We offer Duplex flat heads screws with slotted, phillips and socket head mechanisms. Torx and tamperproof drivers can also be manufactured per drawing. •  ASME B18.3
•  ASME B18.3.6
•  DIN 963 / ISO 2009
•  DIN 965 / ISO 7046
•  DIN 7991 / ISO 10642
Hex Cap Screw    Hex Head Cap Screws Duplex hex head cap screws feature an added washer face and tighter dimensional tolerances compared to a hex head bolt. Best for high clamping force and easy access. • ASME B18.6.3
• DIN 931 / ISO 4014
• DIN 933 / ISO 4017
• DIN 961 / ISO 8676
pan head screw s    Pan Head Screws Duplex pan head screws feature a rounded top and are best used for small diameter uses. We offer both slotted or phillips driver – depending on the size and length of the fastener. • ASME B18.6.3
• DIN 7985
• DIN 921
• DIN 85 / ISO 1580
• DIN 84 / ISO 1207
  (cheese head)
• DIN 966 / ISO 7047
  (raised counter sunk)
SecScrew Drives   Security Screws Duplex tamper proof screws are available in a wide range of driver designs. They provide resistance to unwanted removal – as they are inaccessible with a common screw driver.  
Self Drilling Screw angled image  Self Drilling Screws Available in diameters from #4- 3/8” and  4-10mm, Duplex self drilling screws have both a drilling and fastening mechanism all. • ANSI B18.6.4
• DIN 7504
Set Screw    Set Screws Duplex set screws can be made with a cup, cone, flat, dog and half-dog points. They have no head and feature a socket or slotted driver at one end. • ASME B18.3
• DIN 913 / ISO 4026
• DIN 914 / ISO 4027
• DIN 915 / ISO 4028
• DIN 916 / ISO 4029
Socket Head Cap Screw Short Image     Socket Head Cap Screws Duplex socket head cap screws offer a safe, reliable fastening solution for situations with limited access / clearance around the screws. Duplex socket heads are an economic fastener. • ASME B18.3
• DIN 912 / ISO 4762
• DIN 7984
Vented Screw Main Image short    Vented Screws Duplex steel vented screws are ideal for high vacuum environments because they feature a hole drilled through their axis (from head to thread end) which allows gases/contaminents to vent and relieve pressure. Vented screws can be made in any style.  

Duplex Steel Bolts

Hex Bolt    Hex Head Bolts Duplex hex head bolts are an economic solution when high clamping force and easy access are needed. They are like hex head cap screws, but without the washer face. • ASME B18.2.1
• DIN 931 / ISO 4014
• DIN 933 / ISO 4017
Shoulder Bolt    Shoulder Bolts

Duplex shoulder bolts consist of a head, shoulder and threaded segment. The smooth shoulder section allows for rotating parts. These Duplex bolts are most commonly offered with socket drivers.

• DIN 7379 / ISO 7379
• ISO 7370
Wedge anchorWedge Anchor Bolts Duplex wedge anchor bolts (also known as anchor studs), offer one of the most secure fastening solutions for attaching materials to concrete when high strength is needed.  

 Duplex Nuts

Hex Nut       Hex Nuts

Duplex nuts are available in a variety of styles: finished hex nuts, jam nuts and heavy hex nuts.

• ASME B18.16.3
• ASME B18.2.2
• DIN 439 / ISO 4035
• DIN 934 / ISO 4032
• DIN 986
Lock Nuts       Lock Nuts Duplex lock nuts are can be made in both all-metal (flexloc, top lock, stover) and polymer insert styles. All-metal Duplex lock nuts are ideal for high temperatures. Polymer insert styles are more economical and are best for temperatures under 350°F. • ASME B18.16.3M
• DIN 980 / ISO 7042 / 
   ISO 19513
• DIN 6923 / ISO 4161
• DIN 985 / ISO 10511 /
  ISO 7040

  Duplex Studs & Threaded Rod

Studs    Studs Duplex studs are fully threaded or partially threaded fasteners that are made to custom lengths under 1ft (12 inches). • ASME B18.31.2
• DIN 976
Threaded Rod 2    Threaded Rod Duplex threaded rod are fully threaded lengths of rod that are greater than 1 foot. Our minimum order quantity is a total of 6 feet of rod (1 x 6ft rod, 2 x 3ft rods, etc). • ASME B1.1
• DIN 975
arc and capacitor no text    Weld Studs Duplex weld studs can be made in both arc and capacitor discharge (CD) styles. Weld stud fasteners create an extremely secure fastening solution for permanent attachments when there is only one side of the application that is accessible.  

Duplex Washers

Washer      Flat Washers
Duplex washers are available in SAE, USS, oversized and custom sizes upon request. • ASME 18.21.1
• DIN 125 / ISO 7089 /
  ISO 7090
• DIN 126 / ISO 7091
Lock Washer      Lock Washers
Duplex split lock washer as well as Belleville spring lock washers can be made in common and custom sizes. • ASME B18.21.1
• DIN 127 / ISO 7090
• DIN 6796 /  ISO 10690

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