Dry Film Thickness

The application of coatings to steel surfaces is the most widely used method of protecting against corrosion. Nearly every steel structure has some corrosion protection in the form of paint or coating. These coatings serve various purposes, including corrosion protection. However, it is important for the applied and cured coating to impede the passage of ions, oxygen, and water down to the substrate. The dry film thickness of the coating plays a crucial role in this process.

To ensure maximum performance, coating suppliers have developed products with an optimal dry film thickness. Applying a coating that is too thin can result in rust rashing, which is the formation of numerous small rust spots that spread across the surface, making it difficult to distinguish individual spots. On the other hand, applying a coating that is too thick can lead to solvent entrapment and stress within the coating, ultimately causing adhesion failure in the form of blisters, delamination, or cracking.

Coating surveyors need to be familiar with the products and potential issues related to thickness variations. Although repeatedly applying coatings for maintenance or aesthetic purposes may initially extend the service life of a structure, it can ultimately compromise the entire coating system. Adhesion failures caused by internal stress from the application of additional coatings are commonly observed in maintenance contracts.

The Coating Radar App provides comprehensive information on the process and standards for measuring dry film thickness.