Pigment leaching is the process where inhibitor pigments in a coating are released into the surrounding environment through surface defects.
Here's a more detailed explanation:
Pigment leaching occurs when protective coatings develop imperfections. These imperfections, often microscopic breaks or defects at the surface, expose the underlying inhibitor pigments directly to the elements (water, air, etc.). The leaching process starts when:
- Direct Contact: Inhibitor pigments come into direct contact with the environment through surface-breaking defects in the coating.
- Connectivity: Leaching continues as long as a connected cluster of inhibitor pigments remains exposed. This means that the pigments must be physically connected to each other and to the defect for the process to proceed.
- Loss of Connectivity: Leaching stops when the three-dimensional connectivity of the pigment cluster is broken. In essence, the connected path for the pigments to escape is severed.
Therefore, pigment leaching is a degradation mechanism that reduces the effectiveness of protective coatings over time. The rate of leaching depends on factors like the type of pigment, the severity of environmental exposure, and the nature of the coating.
