The chemical composition of N04400 alloy is mainly composed of 30% Cu and 65% Ni with a small amount of Fe (1%-2%). Due to the difference in chemical composition, it can have a variety of combinations, but there is no significant difference in corrosion resistance between them. N04400 alloy is more resistant to corrosion by reducing media than pure nickel, and more resistant to corrosion by oxidative media than pure copper.

The structure of N04400 is a typical single-phase austenite structure. Since nickel and copper are mutually soluble in any proportion, there is generally no intermetallic phase precipitation. The microstructure of this alloy is observed under non-etching conditions under a metallographic microscope, and it can be seen that there are very dispersed non-metallic inclusions, such as sulfides and silicates, on the austenite matrix. Carbides may also be observed under certain conditions.