Porous or pinhole surfaces on paint coatings are common construction issues, with diameters ranging between 80-120μm. Paint films with such issues can be easily penetrated by external moisture during use, especially in high humidity conditions, which can seep through these small holes and erode the base material, leading to the formation of pores or pinholes in the coating.
There are many reasons that can cause pinhole phenomena in the coating film, such as: the spray gun being too close to the surface, resulting in excessive atomization pressure; high hydraulic pressure leading to insufficient atomization; improper paint formulation; or an unsuitable surface condition for spraying. The specific reasons include the following:
1. Constraints from residual water
The coated substrate surface retains a significant amount of moisture. After application, due to the low boiling point of water molecules, they evaporate from the inside out at the drying temperature, ultimately breaking through the paint film surface to form air holes or pinholes.
2. The Impact of Drying Agents
Due to the rapid evaporation of the surface solvent, the surface paint film dries too quickly, reducing the gaps within the film. This prevents the solvent in the inner paint layer from fully evaporating from the remaining spaces, leading to the solvent bursting through the film, creating air bubbles or pinholes.
3. The Impact of Baking Temperature
Excessive drying temperature causes a large number of solvent molecules to volatilize, preventing a sufficient amount of solvent molecules from passing through the paint film in one go. This leads to some solvent molecules breaking through the paint film, forming air bubbles or pinholes.
4. Influence of Paint Viscosity
High paint viscosity leads to slow solvent evaporation, causing solvent molecules to break through the paint film, forming pores or pinholes. Therefore, it is essential to control the paint film viscosity within a reasonable range.
5. The Impact of Spray Thickness
When the underlying solvent evaporates over a longer distance to the surface, the film gaps are discontinuous, leading to pinholes and air pockets breaking through the coating.
That concludes our discussion on the causes of pinholes in paint coatings from Qianshan Paints. To improve this defect, it is essential to address the root causes of film defects. By conducting a series of analyses, we can identify reasonable solutions. We remind all customers to pay attention to the compatibility between coatings when selecting matching paints to avoid other film defects caused by incompatibility.