Coating precipitation and its causes

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This post was last edited by Wang Wei2 on 2026-2-15 at 10:46. 1. Coating sedimentation (also known as settling) refers to the phenomenon where its solid components (such as pigments and fillers) sink to the bottom of the container over time when left undisturbed. It’s not that all coatings are “problematic”; rather, it is a common physical phenomenon influenced by various factors such as density differences, viscosity, and dispersion stability. Whether intervention is needed depends on whether uniformity can be restored through stirring. 2. Reasons for precipitation and caking: (1) Properties of the pigments and fillers themselves: high density (such as zinc powder, iron oxide mica, red lead), large particle size, and poor wettability, which can accelerate sedimentation ； ⑵Formulation and process defects: an excessive pigment-to-resin ratio (>2∶1), insufficient resin content, and excessive solvents resulting in low viscosity, which leads to a loss of suspension capability ； ⑶Uncontrolled storage conditions: temperature > 30°C, prolonged standing, failure to invert/shake regularly, disrupting the colloidal stability system ； ⑷Chemical incompatibility: Reactive pigments (zinc powder, aluminum powder, zinc oxide) react with certain resins or impurities, resulting in the formation of gels or lumps.