A mid-ranged corrosion resistant 6Mo alloy with good strength

• Good corrosion resistance to moderate acids & sea-water 
• 50% stronger  than stainless steel
• Usable temperature limit of 1000°F
• AL6XN chemistry & specifications
• Hex head bolt features and benefits
• AL6XN Datasheet

Originally developed to combat sea water corrosion, AL6XN has expanded its role as being good mid-range corrosion resistant alloy. AL6XN hex head bolts are a low carbon, high purity, nitrogen-bearing "super-austenitic" stainless alloy. Also considered a 6Moly alloy, AL6XN bolts are similar in chemistry 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

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, hex head bolts 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 hex head bolts outperform so many alloys providing protection to stress corrosion cracking, pitting and crevice corrosion in a broad range of marine applications. AL6XN hex head bolts 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

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 hex head bolts good high strength properties

AL6XN Applications
•  Desalination plants depend on AL6XN hex head bolts for the salt water corrosion protection
•  Pulp bleaching equipment and piping 
•  The power industry uses AL6XN hex head bolts 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 Bolt Types: Hex Bolts, Shoulder Bolts

AL6XN Hex Head Bolt Features and Benefits

It is important to differentiate between a AL6XN hex head bolt and hex head cap screw. Often people assume they are the same, but they are actually very different fasteners in terms of how they are manufactured, as well as from an application perspective. Regardless of your choice, AL6XN hex heads offer strong, stable joints because of their large head service. 

The Hex Comparison

AL6XN Chemical Composition & Specifications

AL6XN Specifications: UNS N08367, 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

AL6XN Mechanical Data

Corrosion Curves for AL6XN