What is Coating Porosity and How to Detect

       Coating porosity is a unit of measure describing coating density and one of the quantitative indicators reflecting coating quality. Porosity is the number of pores per unit area in the coating to the primary channel, expressed as pores/cm2. Porosity is also measured by the ratio of the volume of pores on the coating material to the geometric volume of the coating, expressed in %, which is the product of the thickness of the coating and its area. In addition, the density ratio (coating density/actual density of coating material) is also used to express porosity. It is determined by measuring the density of the coating compared to the density of the original coating material before spraying.



    The porosity of the coating can directly affect the protective performance of the coating. As a wear-resistant coating, the pores in the coating can be used to preserve lubricants, accommodate abrasive particles, and make the coating more wear-resistant. However, if it is used in abrasive or corrosive working conditions, the corrosive medium will penetrate into the surface of the substrate through the holes, which will not only harm the corrosion resistance, but also reduce the bonding strength and be prone to peeling. For coatings used in environments such as heat and corrosion resistance, porosity must be measured.

    There are many methods for detecting coating porosity. According to the physical definition of coating porosity, the direct measurement methods include: buoyancy method, direct weighing method, etc.; chemical corrosion methods include: paste coating method, filter paper method, dipping (perfusion) method ; In addition, there are electrolytic imaging method, microscope method, electrolytic coloring method, penetrating liquid and weighing method, high voltage discharge method, etc.