Characteristics of coating bubbles

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Coating bubbles are bubble-like defects that appear on the surface of the coating; they represent a thermodynamically unstable two-phase system formed by gas within the coating liquid. Their presence increases the surface area of the coating and the energy of the system, while the breakdown of these bubbles leads to a decrease in energy, indicating that the system is in an unstable state. The interior of the bubble can contain liquid, vapor, gas, or crystals, and its size is related to the adhesion of the coating, the internal pressure, and the degree of stretching of the coating film. Based on their morphology, they can be divided into two categories: Bubbles refer to individual spherical microbubbles, which are commonly found in solvent-based coatings. Foam: Formed by the accumulation of dense clusters of bubbles on the surface of a liquid, and is commonly found in water-based coatings. Bubbles can severely affect the appearance and performance of the coating, causing surface defects such as pinholes, pitting, and orange peel texture; they also reduce the coating’s corrosion resistance, weather resistance, and adhesion, making them a key issue in coating quality control.