Thermal sprayed coatings always exhibit a certain amount of porosity. The permeability of the coating increases with higher porosity, the degree of which can be controlled in coatings of metallic and ceramic materials. At the same time, the coating must remain structurally sound, and the porosity be homogeneously distributed throughout the coating. Some examples of coating applications requiring a high amount of controlled porosity is clearance control coatings (abradables), and oxygen sensors for automotive engines, where a permeable coating is used to control the oxygen that reaches the sensing mechanism.

Sulzer Metco offers a large number of coating-systems for different functions.