Monel 400 is a combination of nickel and copper and is hardened by cold working only. This alloy is widely renowned for for its corrosion resistant properties against flowing sea - water and is extensively used for marine applications. Monel is also extremely resistant to stress corrosion cracking in most freshwaters. High temperature ( up to 1000 °F) has no effect on this alloy and it also has excellent mechanical properties at subzero temperatures.