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Coatings · Surface Defects · Leveling · DH-3077
When cratering and fish-eye surface defects appear during coating application, the problem is often described as "leveling is insufficient." But in actual formulation adjustment it is frequently found that some coating films look quite flat after application — yet cratering still appears during drying. This is related to the surface state of the coating liquid when spreading. From spray application to forming a continuous coating film, the process involves wetting, spreading, flowing, and curing. If the wetting relationship between the coating liquid and the substrate does not match, or local surface tension differences are large, the coating liquid may not spread uniformly. Therefore, when addressing cratering and fish-eye, in addition to focusing on leveling speed, the influence of the additive on substrate wetting and subsequent recoatability also needs to be observed.
Four Common Problems
Good Coating Flow — But Cratering Still Appears
Leveling primarily addresses surface flow after film formation. Substrate wetting occurs earlier. If the coating liquid cannot spread in time after contacting the substrate, a locally under-wetted state may form. Even if subsequent flow is good, it may not fully compensate for the interfacial differences that formed at this earlier stage.
Same Formulation — Different Appearance on Different Substrate
Different substrates differ in surface state, so the wetting relationship between coating and substrate also changes. The same coating may spread normally on one substrate but develop cratering, fish-eye, or localised retraction on another — which is why formulation testing cannot only look at the coating liquid itself but must be evaluated in combination with the specific substrate.
Leveling Improved — Recoating Develops Problems
Some surface additives act strongly on the film surface. If the usage method or addition level is not suitable, the interface state of the subsequent coating layer may change. So when evaluating a leveling agent, not only the first coat appearance should be observed — recoat testing is also needed to confirm whether the second coat can spread normally, adhere, and form a uniform surface.
Cratering and Fish-Eye Appear Together
Though different in visual appearance, both may relate to the interface state during coating liquid spreading. When the wetting relationship between coating and substrate is not ideal, or surface tension distribution has differences, the coating liquid may retract in localised areas — forming different degrees of surface defects. In formulation adjustment, "substrate wetting" and "surface flow" can be observed together.
Adjustment Approach: Wetting First, Then Leveling
For these problems, the film formation process can be split into two stages.
Stage 1 · Substrate Wetting
After the coating liquid contacts the substrate, it needs to spread and form a continuous coverage state. If a problem exists at this stage, subsequent leveling performance may also be affected — regardless of how good it is.
Stage 2 · Film Flow
As solvent evaporates and the film gradually forms, the coating surface still undergoes a degree of flow. Appropriate surface flow helps improve film flatness and reduces local surface differences.
Therefore, leveling agent selection is not simply pursuing "faster flow" — its comprehensive influence on substrate wetting, surface state, and recoat performance needs to be observed.
DH-3077: Fluorine-Modified Acrylate Copolymer Leveling Agent
DH-3077 is a fluorine-modified acrylate copolymer leveling agent, primarily addressing the interfacial state between the coating liquid and substrate, helping to improve the spreading process. In actual application, it can be evaluated from the following directions:
①
Improving Coating Spreading
DH-3077 has good surface flow capability, helping the coating liquid spread toward the surrounding area during application — allowing the film to form a more uniform surface state.
②
Improving Substrate Wetting
For some substrates that are more difficult to wet, an appropriate addition can improve the contact state between coating liquid and substrate. After substrate wetting is improved, localised surface defects such as cratering and fish-eye also have the opportunity to improve.
③
Accommodating Recoat Requirements
For coating systems requiring multiple application passes, the first coat surface state affects subsequent coatings. While improving wetting and leveling, DH-3077 has relatively limited influence on recoat application — so it can be used with combined recoat testing for the specific system.
④
Long-Term Film State
DH-3077 adopts a fluorine-modified acrylate copolymer structure with good light resistance and ageing resistance, and is not easily hydrolysed. In some formulations it can also provide a certain plasticising effect.
Addition Level and Testing Approach
Recommended addition: 0.2%–1% of total formulation. In actual application, direct addition at a fixed ratio is not recommended — gradient testing should be performed based on resin type, substrate, application method, and film thickness.
| Coating spreading state | Observe whether the coating liquid spreads uniformly and whether local retraction occurs |
| Cratering and fish-eye | Compare defect frequency and severity at different addition levels |
| Film flatness | Observe surface leveling state after drying |
| Substrate wetting | Check whether coating forms continuous coverage at the substrate interface |
| Recoat surface state | Confirm whether the second coat spreads normally after the first coat cures |
| Film adhesion | Check cross-cut and tape adhesion under the actual application conditions |
Especially for formulations that already have cratering problems, the appropriate balance can be found by gradually adjusting addition level — rather than simply raising the additive proportion.
Summary
When cratering and fish-eye appear in a film, leveling is only one observation direction. Whether the coating liquid can adequately wet the substrate, whether it spreads uniformly after application, and whether the interface state changes during subsequent recoating are all equally worth attention. For these problems, formulation adjustment can be judged from three aspects: substrate wetting, surface flow, and recoat performance. DH-3077 fluorine-modified leveling agent can be used to improve substrate wetting and film leveling while accommodating subsequent recoat requirements. The specific addition level needs to be tested in combination with the actual formulation and application conditions.
Frequently Asked Questions
Why does fluorine modification specifically improve substrate wetting compared to standard acrylate leveling agents?
Fluorinated groups have the lowest known surface energy of any organic functional group — significantly lower than standard hydrocarbon or silicone groups. When a fluorine-modified leveling agent concentrates at the film-air and film-substrate interfaces during application, it reduces the surface tension of the coating liquid at the substrate contact zone more effectively than standard acrylate structures. This reduced interfacial tension makes it easier for the coating to spread and establish contact with difficult-to-wet substrates — which is the mechanism behind the improved cratering resistance on challenging substrate surfaces.
Why does DH-3077 have "relatively limited influence on recoat" compared to silicone-type leveling agents?
Silicone-type leveling agents have very strong surface migration tendency and form a distinct silicone-rich layer at the film surface — this layer has very low surface energy and poor chemical compatibility with subsequent coating layers, which is the primary mechanism causing poor interlayer adhesion after silicone-type leveling agent use. Fluorine-modified acrylate structures, while also surface-active, form a less pronounced and more chemically compatible surface layer than silicone — reducing the wettability and adhesion impact on subsequent coatings. The specific recoat performance should still be confirmed for the particular multi-coat system through testing.
