Uneven Coating Spread May Point to a Substrate Wetting Problem

After application, the film surface may show pinhole-like depressions, local shrinkage and uneven spreading. These defects affect appearance and also add to rework and formulation adjustment.

Adjusting the leveling additive is a common approach. However, the state of the film does not depend on leveling ability alone. Whether the substrate is easily wetted by the coating, whether the components suit each other, and whether application and drying are stable all affect the final result.

In primer and topcoat systems, multi-pass spraying or recoating, the appearance of the first film is only part of the evaluation. While improving spread, the additive must also allow the following coat to be applied normally and the interlayer bonding to meet requirements.

Once sprayed on a workpiece, the liquid layer flows, evaporates and forms the final appearance. If surface tension differs locally, the liquid can flow unevenly, causing local shrinkage or depressions. Oil, cleaner residue or insufficient surface treatment on the substrate can also affect spreading. When craters appear, check both the substrate and the formulation conditions rather than simply blaming a shortage of leveling agent.

A leveling additive influences the surface state of the coating, but different resins, solvents and additives interact differently. If the system is poorly matched, raising the dosage may not bring lasting improvement. In small trials, compare surface defects, leveling and storage changes at different addition levels. If appearance improves little as the dosage rises, or other properties change, re-evaluate how well the additive fits the system.

A smooth first film does not guarantee that the second coat will spread well. Dryness of the lower layer, its surface state, the recoat interval and the composition of the next coating all influence the result. For multi-pass systems, verify recoat appearance and interlayer adhesion under real process conditions instead of judging only by first-film leveling.

Confirm the source of the defect. See whether defects concentrate on a specific substrate, on workpiece edges or in a particular application batch, and review cleaning, degreasing and surface treatment.

Check the application process. Consider spray method, film thickness, flash-off time and drying conditions to judge whether the defect relates to application parameters.

Compare dosages. With other conditions kept as consistent as possible, set different additive levels and compare spreading, crater count and surface state.

Add a recoat test. For systems with recoat requirements, apply a second coat using the real interval and drying conditions, then observe surface defects and interlayer adhesion.

DH-3077 is based on a fluorine-modified acrylate copolymer and suits formulations that need better leveling, substrate wetting and recoat performance.

Start by evaluating at 0.2% of the total formulation, then adjust step by step according to the film. Record craters, leveling, recoat appearance and interlayer adhesion so that overall performance can be compared at each level. Because resin type, solvent composition and application conditions differ, the exact dosage still has to be verified in the real system. If the problem mainly comes from substrate contamination or the application environment, adjusting the additive is usually not enough to remove all defects.

Is a shortage of leveling agent the reason for craters? Not necessarily. Substrate oil, cleaner residue or insufficient surface treatment can also affect spreading, so check the substrate and formulation together.

Why might a higher dosage not help? If resin, solvent and additive are not well matched, raising the amount may not give lasting improvement. Re-evaluate the fit when appearance barely improves.

Does a smooth first coat guarantee good recoating? No. Lower-layer dryness, surface state, recoat interval and the next coating all matter, so verify recoat appearance and adhesion in the real process.

What dosage is recommended for DH-3077? 0.2%-1% of the total formulation. Trials can start at 0.2% and be adjusted according to film state, with the final amount confirmed in the actual system.