A mid-ranged corrosion resistant 6Mo alloy with good strengthAL6XN Pixabay Free Valve

Originally developed to combat sea water corrosion, AL6XN has expanded its role as being good mid-range corrosion resistant alloy. AL6XN fasteners are a low carbon, high purity, nitrogen-bearing "super-austenitic" stainless alloy. Also considered a 6-Moly alloy (6% Molybdenum), AL6XN bolts are similar in composition and capabilities to Alloy 926 and SMO 254. With a higher nickel and molybdenum content than Duplex 2205 and Super Duplex 2507, it delivers better corrosion resistance while giving a more cost effective alternative to nickel super alloys like Inconel or Hastelloy in moderately corrosive conditions.

Corrosion Resistance
•  Moderate general corrosion resistance
•  Excellent chloride / salt water protection
•  Good performance in phosphoric acid
•  Moderate resistance to nitric acid

AL6XN Corrosion Comparison

Chemical Resistance
In chemical processes which utilize chlorides, such as paper mills and waste water, stress corrosion cracking (SCC) is a common culprit for 316L stainless failures. Duplex alloys will outlast environments that will cause SCC in 316 stainless, but for more severe low PH environments, fasteners made from higher nickel content alloys like AL6XN will generally work better. For the most extreme situations, alloys with >45% nickel content like Hastelloy are often considered.

Outstanding Resistance to Salt Water
Seawater is where AL6XN outperforms so many alloys providing protection to stress corrosion cracking, pitting and crevice corrosion in a broad range of marine applications. AL6XN fasteners contain a minimum of 6% molybdenum content and it is this addition of molybdenum that provides the greatest protection against pitting and crevice corrosion.

Mechanical Properties
Electrical Resistivity: 535 Ohm-circ mil/ft
Ultimate Tensile Strength: 108 ksi
0.2% Yield Strength: 53 ksi
Density: 0.291 lb/in 3

AL6XN strength Comparison v2

Chemistry
•  High molybdenum content provides enhanced corrosion protection in chloride environments.
•  Carbon helps to prevent sensitization during welding
•  Chromium enhances pitting and crevice corrosion resistance
•  The interstitial strengthening effect of nitrogen gives AL6XN good high strength properties

AL6XN Applications
•  Desalination plants depend on AL6XN for the salt water corrosion protection
•  Pulp bleaching equipment and piping
•  The power industry uses AL6XN screws where salt water and chlorides are present such as steam surface condensers, supercritical, high pressure, feed water heaters, steam surface condensers, flue-gas desulfurization equipment and in nuclear power water piping
•  Offshore
•  Chemical Processing - processing tanks, vessels and pipes as well as plate and frame heat exchangers.

Resources: AL6XN Torque Specs

AL6XN Fastener Types: Bolts, Nuts, Screws, Studs, Threaded Rods, Washers


 

AL6XN Chemical Composition & Specifications

AL6XN Specifications: UNS NO8367, ASTM A 240, ASTM B 688, ASME SA-240, ASME SB-688, ASTM B690, ASTM B691, ASTM A240, ASTM B688, ASME SA-240, ASME SB-688

June 2020 AL6XN Chemistry

 


AL6XN Mechanical Data

 June 2020 AL6XN Tensile Data


 Corrosion Curves for AL6XN

June 2020 AL6XN HCL Curve

 

June 2020 AL6XN Sulfuric Acid Curve

 

June 2020 AL6XN Phosphoric Acid Curve

 

AL6XN Corrosion Resistance in Boiling Solution June 2020 Version 2

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