Generally speaking, common cerium oxide has cerium trioxide and cerium dioxide. They are widely used in semiconductor materials, pigments and sensitizers for photosensitive glass, automobile exhaust purifiers.

1. Cerium trioxide has a hexagonal structure of rare earth sesquioxide, which is sensitive to air and is mainly used as a catalyst.

2. Cerium dioxide is the most important and representative oxide of cerium, which is insoluble in sulfuric acid and nitric acid. Cerium dioxide can be made by heating cerium hydroxide or cerium oxalate in the air.

The best example of cerium coatings against oxidation and corrosion begins with the alloys where cerium dioxide is used to form chrome-oxide coatings. There are many techniques for coating alloys with cerium oxide, including spraying, impregnating in cerium nitrate solutions, sputtering, and electrophoresis. Adding a small amount of cerium to high-strength low-alloy and stainless steel can improve grain boundary stability and control the shape of sulfides during steel manufacturing. Cerium is often added to molten steel in the form of a cerium-rich mix of rare-earth metals, where it combines with oxygen and sulfur to produce cerium oxides and cerium oxides with high melting points and hardness to avoid the formation of other oxides and sulfides with poor properties. The rare earth inclusions do not deform during rolling, thus giving fine grained final products good properties.