Noun
ferrous oxide (uncountable)
English Wikipedia has an article on:ferrous oxideWikipedia
(chemistry) The chemical compound FeO, iron oxide where iron has a valence of +2.
For such iron-rich rocks to be deposited there would have to be anoxia in the ocean, so that much dissolved iron (as ferrous oxide ) could accumulate before it met an oxidant that would precipitate it as ferric oxide. Source: Internet
It helps to have the iron oxide as ferrous oxide (FeO) which is obtained via slight reducing conditions i.e. operating with zero excess oxygen at the kiln exit. Source: Internet
The conversion of the passivating ferrous oxide layer to rust results from the combined action of two agents, usually oxygen and water. Source: Internet