Z 2 NCDU 25.20 is AFNOR name for 904L (AISI) or 1.4539
In AFNOR code, Z stands for stainless steel. First number stands for percentage of carbon x 100 (i.e. 10 means 0.1% of Carbon)
here we have less than 0.02% for Z2 and less than 0.01% for Z1
Cyril Guichard
Mechanical Engineer Consultant
France