Automotive Coatings
Automotive coatings are thin, highly exposed films, so the colour paste has to deliver light fastness, batch-to-batch colour agreement and dispersion fine enough for gloss and distinctness of image. The paste must also remain compatible with the acrylic, polyester or alkyd binder and with the solvent balance of the finished system, because any flocculation or seed shows up directly as orange peel, haze or a shade drift after baking. Because the same colour may be used on an OEM line and in a refinish workshop, the paste also has to behave predictably across very different film builds and drying conditions.
Key Requirements in This Application
Weather resistance and light fastness
Exterior films are exposed to UV, moisture and thermal cycling for the life of the vehicle. Pigments and carriers must be selected so that the cured film resists chalking, gloss loss and shade shift, and the paste must not introduce components that accelerate degradation of the binder under QUV or xenon exposure.
Batch-to-batch colour agreement
Refinish and OEM lines match against approved colour standards, so the paste must reproduce the same chroma and hue from lot to lot. This depends on pigment selection, consistent dispersion fineness and a controlled let-down ratio rather than on visual adjustment at the mixing stage.
Dispersion fineness and gloss
Undispersed agglomerates scatter light and reduce gloss and distinctness of image in a thin automotive film. Grinding must reach a fineness and particle size distribution that keeps the film optically clean, which is measured by scraper fineness and laser diffraction rather than judged by eye.
Binder and solvent compatibility
The carrier must be compatible with acrylic, polyester and alkyd binders and with the ester, ketone and aromatic solvents used in the let-down. An incompatible carrier produces craters, poor flow or a co-solvent window that collapses during flash-off and causes flooding in the drying film.
VOC and solvent balance
Solvent-borne systems are formulated within a defined VOC target, so the solvent carried in by the paste has to be counted in the total. Pastes that contain a high proportion of slow solvent change the evaporation profile and can extend tack-free time or trap solvent in the film.
Storage behaviour in workshop quantities
A refinish workshop may use a can over several weeks, so the paste must resist hard settling, skinning and viscosity drift in partly used containers. A paste that has to be vigorously stirred before every tint introduces a variability that is difficult to control, and settled pigment can change colour strength between the first and last mix of the same can.
Repairability and blendability
Spot repair requires the repaired area to blend into the original panel without a visible halo. That depends on the paste producing a consistent opacity and transparency at the film thickness used for blending, so the same colour can be faded out at the edge rather than matched as a hard boundary.
Recommended DENSON Series
Oil-based colour pastes built for solvent-borne systems, with roughly 20 percent PMA in the carrier; they let down cleanly into acrylic, polyester and alkyd binders and tolerate the ester and ketone blends used in refinish tinting. They are solvent-borne and must not be described as solvent-free.
View seriesResin-free carrier pastes with a high pigment load, which give formulators room to set their own binder level and let-down ratio in universal and refinish systems. Because the carrier adds no resin of its own, the finished binder system stays under the formulator's control; the carrier still contains solvent.
View seriesTechnical Considerations
- Confirm the let-down ratio against the required film colour before tinting, because automotive films are thin and small dosage errors shift the shade visibly.
- Add the paste during pre-dispersion rather than at let-down, so the pigment surface is wetted before the binder competes for it.
- Check the co-solvent window against the binder: a carrier whose solvated chain collapses early during flash-off tends to flood or float in the drying film.
- Control spray viscosity and film build together; the same paste at a different film thickness reads as a different colour.
- Re-run the colour match after any pigment lot or binder grade change instead of assuming the previous dosage still applies.
- Verify intercoat compatibility with the clearcoat before approving a colour, because adhesion and recoating behaviour are decided at the interface rather than by the base coat shade.
Testing and Compliance
Dispersion quality
Scraper fineness to GB/T 6753.1, paste viscosity to GB/T 9751 and particle size distribution by laser diffraction to ISO 13320. These three together decide whether the film will be optically clean.
Colour and appearance
Colour difference against the approved standard is measured instrumentally on a cured draw-down, with gloss and distinctness of image checked on the same panel so that dispersion faults are not mistaken for tinting faults.
Durability
Accelerated weathering by QUV or xenon arc, together with humidity and thermal cycling, is used to confirm that the pigment and carrier combination holds gloss and shade over the service life expected of the coating.
Storage and redispersibility
Elevated-temperature storage is followed by manual redispersion to confirm that the paste does not skin, hard-cake or drift in viscosity over the period a workshop or warehouse would realistically hold the container.
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Tell us the resin system, process conditions and performance target, and we will confirm the suitable series and starting dosage.
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