AL-6XN alloy is resistant to a broad range of corrosive environments. Processes with chloride-induced corrosion in the forms of pitting, crevice and stress corrosion cracking in 300 series stainless steels are often better managed with AL-6XN alloy. AL-6XN alloy is also resistant to corrosion from various acids and salt solutions. This is due to the higher concentrations of the following elements in the alloy:
- Nitrogen which retards the formation of chi phase during manufacturing and field welding
- Chromium provides good resistance to oxidizing environments
- Molybdenum improves resistance to chlorides.
AL-6XN alloy initially is more expensive than 300 series stainless steels. However, life-cycle costs for systems utilizing the alloy can be far less than the comparable costs of the initial installation, maintenance, and subsequent replacement of lesser alloys used in aggressive environments.
In addition to material replacement, labor costs, and production downtime caused by system failures in corrosive environments, consideration must also be given to the associated costs of product contamination caused by corrosion. Studies have shown the initial cost comparison of AL-6XN raw material to other alloys as follows:
- 304L stainless steel = factor of 1 (base)
- 316L stainless steel = 1.15x 304L stainless steel
- AL-6XN Alloy = 3x 304L stainless steel
- C-276 / C-22 = 5x 304L stainless steel
Note: The cost comparison shown above is an approximation and may vary greatly depending on the specific product.
When selecting materials for process systems, guidelines should be followed giving consideration to the service environment. The inclusion of corrosion control and the correct material selection is the most efficient and economical means for controlling corrosion and adding life to a piping system.