What is the difference between alloy 28 and alloy 825?
1.4563 – Alloy 28 – Sanicro – N08028
UR 28 is a super-austenitic stainless steel with a very high nickel (31%) and chromium (27%) content. The molybdenum content is approximately 3.5%. The alloy is designed for specific uses, including sulfuric and phosphoric acid applications.
UR 28 performs much better than Alloy 825 and may be considered as an alternative to the more expensive 625 grade in certain applications (sour gases). The alloy is widely used in chemical and offshore applications, including highly sour gas fields.
Alloy UR 28 is more corrosion resistant than Alloy UR 904L (N08904) in most corrosive solutions. This alloy is widely used in phosphoric acid applications and some sulfuric acid solutions.
Alloy UR 28 can also be used in caustic solutions since its molybdenum content remains low compared to nickel and chromium additions.
The addition of high chromium and moderate amounts of molybdenum helps improve the localized corrosion resistance of UR 28 alloy. This grade performs far better than Alloy 825 and also better than Alloy N08904 (UR 904L) in solutions containing acidic chlorides.
The high nickel and molybdenum content gives UR™ 28 excellent resistance to stress corrosion cracking. This is especially true for high temperature applications (140 - 400 degree =284 - 752 degree F) and chlorine containing environments.
UR 28 is particularly suitable for sour gas applications and has been successfully tested at 230 degree (446 degree F), 3 bar H2S and 50 bar CO2 as well as high chloride contents.
UR 28 alloy has been successfully used in the following applications:
