Porosity creates poor coating cohesion and allows for higher wear and corrosion rates. Porosity is generally associated with a high number of unmelted or resolidified particles that become trapped in the coating, as shown in the diagram.
Open porosity can interconnect to the coating interface, enabling corroding or oxidizing elements to attack the base material. Porosity can thus “short-circuit” the inherent corrosion resistance of a coating. For hardface or wear-resistant coatings, porosity lowers coating hardness and contributes to poor surface finishes, thus decreasing wear resistance. Porosity in wear coatings can also lead to the generation of coating fragments that break away and become abrasive cutting agents, increasing coating wear rates.
Volume 5A, Thermal Spray Technology ⇒ Thermal Spray Processes and Coatings ⇒ Coating Structures, Properties, and Materials ⇒ Coating Structures
