Causes and treatment methods of coated pinholes

After the coating is applied, tiny holes appear on the surface, just like the small holes made in paper with a sewing needle, called pinholes.

The appearance of pinholes is mainly caused by two reasons: on the one hand, if the leveling property of the paint itself is not good, after it is applied to the surface, it is not fully fused together, and the gaps left will form pinholes; On the one hand, if the coating contains air and solvent, it will expand after being heated and escape the dry coating surface, and the escape path forms needle-shaped pores. On rough surfaces, such as inorganic zinc coatings, concrete, dry-sprayed surfaces, etc., when the coating is applied, if the coating itself has poor wettability and cannot fully penetrate into the pores, the air will be contained under the coating. When the temperature rises, the air expands and escapes, also forming pinholes.

From the perspective of construction tools, pinholes are most likely to occur when using drums, because radial construction is easy to entrain air, and. Poor wettability to uneven surfaces. When applying by brush, excessive build-up of paint, especially products with poor viscosity and leveling properties, should be avoided. When spraying, pinholes are generally not produced under normal conditions. However, avoid using highly volatile thinners as much as possible in hot and windy weather conditions. In addition, of course, it is necessary to control the appropriate spraying technology to avoid the nozzle being too close to the painted surface or the spraying pressure being too high. When pinholes occur during construction, adding thinner to reduce the viscosity of the coating and increase the fluidity of the wet film is usually a solution.

Once pinholes are observed after the paint film dries, sanding can be used to remove the pinhole coating. Pinholes sometimes only appear on the surface layer, sometimes they may penetrate several degrees of coating to the substrate, so the principle of grinding is to not see the pinholes. After removing the pinholes, reapply the corresponding coat according to the number of coats removed.