Orange peel (effect)

In surface finishing, the term "orange peel" refers to a surface defect resembling the texture of an orange peel. It is characterized by an uneven, wavy, or dimpled appearance on a coated surface. This effect is undesirable as it reduces the aesthetic quality and smoothness of the finish.

Orange peel can occur in a variety of coating applications, including painting, powder coating, and other types of surface treatments. Several factors can contribute to its formation. These include:

• Improper viscosity: Coatings that are too viscous (thick) may not flow out smoothly, leading to uneven surface tension and the formation of the orange peel texture. Conversely, coatings that are too thin may sag or run, also causing irregularities.

• Incorrect application technique: Spraying techniques that are too rapid, use incorrect nozzle settings, or employ inconsistent distances can create uneven coating thickness and result in orange peel.

• Inadequate substrate preparation: Contaminants on the surface, such as dust, grease, or oil, can interfere with the coating's adhesion and flow, contributing to the effect. Insufficient surface profiling (e.g., sanding or etching) can also hinder proper adhesion and leveling.

• Inappropriate drying or curing conditions: Temperatures that are too high or too low, or humidity levels that are outside the recommended range, can affect the coating's drying and curing process, leading to uneven shrinkage and the formation of orange peel. Rapid drying can trap solvents in the coating, causing it to shrink unevenly.

• Incompatible solvents: Using solvents that evaporate too quickly or too slowly can affect the coating's flow and leveling properties.

• Coating composition: The inherent properties of the coating material itself, such as its surface tension and thixotropy, can influence its tendency to exhibit orange peel.

Addressing orange peel typically involves adjusting the application process, modifying the coating formulation, or improving substrate preparation. This can include adjusting spray gun settings, thinning the coating with appropriate solvents, ensuring thorough surface cleaning, controlling temperature and humidity, and selecting coating materials with improved flow characteristics. Post-application techniques, such as sanding and polishing, may also be used to reduce the severity of the orange peel effect.