When it comes to metals, there are various types, the most important for Protective coatings being the refractive based metals, and structural metals.  Refractive metals are the most popular in Industrial coatings as they provide a very hard substance, with a very high melting point.  Within this group of metals, you also have Platinum group metals – which are unique as they also combine superior catalytic properties, with low chemical reactivity.  Because of this, this subgroup of metals makes for very good protective coatings against chemical stresses.    For example one of these metals is Tungsten – which has an extremely high melting point of approximately 3410’c and a density of 19.3 g/cm3 which has many uses such as blast shields, furnace shields but also in warhead technology.  The difficulties with metallurgical coatings are because problems happen not so much with the metals themselves, but the way they are applied or the way they are processed into a coating, as sometimes there can be issues with purity in the various processes they go through. Various treatments exist, such as chromiding, metaliding electroforming and electro deposition.

Ceramic Protective coatings are used in severe environments, one of the advantages over metallic coatings is that they deposit at relatively low temperatures – so it is possible to accommodate low melting points of the fabrication The other main bonus is that the coating is fully dense, and there is a wide range of carbides oxides nitrides and borides to choose from.  They are an excellent solution for retarding wear, while retaining very good thermal properties.  The mass of ceramic coatings, is the main attracting factor over the refractive metal based coatings, which show a very high density, comparatively speaking;- the ceramics have similar properties with much lower densities.