1. Incorrect Paint Formulation:​ The component ratio during paint mixing is wrong. For example, insufficient pigment is added, resulting in poor hiding power.
2. Improper Application Parameters:​ The paint’s application viscosity is too low, leading to an overly thin film. Alternatively, the paint was not stirred thoroughly before use, or the specified film thickness was not achieved.
3. Complex Substrate Geometry:​ It is easy to miss areas when coating complex-shaped objects if not done carefully.
4. Color Mismatch:​ Significant color difference between the primer and topcoat can exacerbate coverage issues.

Solutions & Preventive Measures:

1. Use Qualified Paint:​ Use paint with good hiding power. If necessary, blend the defective paint with a qualified paint of the same color and type in a specific ratio, or simply select a paint with stronger hiding power.
2. Adjust Application Parameters:​ Appropriately increase the paint’s application viscosity. Ensure thorough stirring before use, and apply the coating to achieve the specified film thickness.
3. Careful Application:​ Pay close attention during application on complex objects to ensure no areas are missed.
4. Color Coordination:​ Try to use primer and topcoat colors that are similar to each other, or use a primer color that is similar to the substrate’s color.