Coatings is a complex combination of raw materials which must be mixed, applied to a specific substrate, dried and cured under the appropriate conditions in order to achieve their maximum capability. Coatings can be suffered from premature failure or exhibit defects that may or may not result in failure.
| Defects | Appearance | Causes | Remedy |
|---|---|---|---|
Crawling  | Retraction or pulling back, a uniform de-wetting defect. The liquid coatings do not fully wet the substrate, retract and leaving part of substrate naked. | The surface energy of the solid substrate is lower than the surface tension of the liquid coatings. | Ensure proper cleaning on surface of substrate Lower surface tension of liquid coating by addition of wetting agent. |
Crater/Fish eye | Small circular depressions in the surface of coatings. | Normally occurred due to small particles of a low surface tension contaminants(polishing contaminants) on the substrate or that embeds in the coatings | Perform spray booth air filtration and eliminate the contaminants. By adding surface wetting agent (DMS/low Tg polyacrylates) |
Poor Hiding Power | Uneven coating coverage or uneven distribution/dispersion of titanium dioxide, TiO2 | Hard settling of the contents, Uneven or inadequate paint coverage to mask the substrate colour Different types of TiO2 used may affect opacity | Uniform and sufficient paint application to obtain a proper hiding. Addition of dispersing agent during milling process Select high quality TiO2 |
PoorFlow &Leveling | Coatings failed to dry to a smooth film, resulting in roller marks after coatings dried or cured. | High viscosity of liquid coatings Thicker layer of coatings applied will lead to poor flow | Adjust low shear viscosity of paint with appropriate thickener. Use the suitable reducer to adjust viscosity of coatings. |