Definition - What does Ferrous mean?
Ferrous is an adjective used to describe any material, circumstance or design that has an origin in or relationship with the element iron. Iron is a corrosive substance.
Corrosionpedia explains Ferrous
Substances such as stainless steel, cast iron and steel are all primarily made up of iron, and can therefore be described as ferrous in nature.
Understanding Corrosion in Pumps and How to Deal With It