ferrous nitride is an inorganic compound of iron and nitrogen. It is a gray powder that is insoluble in water and can release ammonia when heated. It can be used to form a thin layer on a metal surface that can enhance corrosion resistance in non-oxidising dilute acids or alkali media.

Characteristics of iron nitride are: high corrosion resistance, brittleness and a strong magnetic property. It is also resistant to oxidation at low temperatures (400deg C) and under pressure.

A range of nitride complexes can be obtained with distinct structures and electronic properties. They can include six-coordinate, four-fold symmetric nitrides that have been characterized at cryogenic temperatures. These complexes can also contain tris(carbene)borate nitrides that are isolable, but have a unique reactivity for the synthesis of ammonia through a one-electron pathway.

Nitride-forming alloying elements can be dissolved in ferrite and are the dominant source of hardness enhancement by precipitation hardening. The amount of these nitride-forming alloying elements, as well as the nitriding time and temperature, affects the stress distribution in the diffusion zone.

In the case of plasma nitriding, short treatment durations lead to a thinner compound layer, which is comparable to the effect of a continuous sputtering process. Longer treatment durations lead to a reduction of the thickness of the austenite layer.

During nitriding, Fe3+ and Fe2+ nitrides are formed on the nZVI particle surface, which are very stable and inhibit further corrosion. The nitride surface has a very thin (oxyhydr)oxide layer that is able to prevent the fast corrosion of nZVI particles in water. The nitrided particles are also more resistant to chloride corrosion than pristine nZVI.