The textbook difference between ferrous vs non-ferrous metals is the presence of iron; ferrous metals are those made of or from iron, while non-ferrous metals are those that do not contain iron. Definition.
"Ferrous metals or alloys are those which contain iron (ferrite), such as carbon steel, chromium steel, and stainless steel. On the periodic table of elements, iron is represented with the abbreviation of “Fe” derived from the term Ferrous. The term ferrous is derived from the Latin word “Ferrum”, which is defined as “iron” or “containing iron.” Ferrous materials are those represented by a specification that begins with “SA”, such as SA-516, SA-335, and SA-240.
Non-Ferrous metals are metals or alloys that do not contain iron (ferrite) in appreciable amounts, such as aluminum, Inconel, Hastelloy, and titanium. Non-ferrous metals are those represented by a specification that begins with “SB”, such as SB-209, SB-444, SB-622, and SB-338."
e.g. SB 424 UNS N08825 Appreciable amount of Fe is present in it. (Appreciable, dominating etc. like terms are creating confusion in such cases.) Fe 22% min. but it is non ferrous.