Definition - What does Runs mean?
Runs are the occurrence of a paint defect in which the applied paint does not adhere uniformly to the surface being coated, rather it flows downward forming a teardrop-like distribution. Such paints are applied to metal surfaces as protective coatings against corrosion.
Corrosionpedia explains Runs
Runs are problematic during the process of applying protective coatings. They are usually due to the use of excessive paint film in each application, excessive film dilution or inadequate prior surface preparation.
Runs can be prevented by the following methods:
- Painting successive thinner films instead of fewer thicker films, checking with a wet film thickness gauge if necessary
- Proper surface preparation
- Better dilution ratios of chemicals or paint to water
Coagulation may occur when runs form. This is due to the molecular structures and physical properties of the components. Coagulation makes spray application, surface modification and paint removal more difficult. Therefore, coatings must be applied after initial mixing but before the onset of coagulation and/or the fluid separation of coating components.