Untergrundhaftung
Kein Haftgrund
Fehler beim Füllern

Detachment from the substrate

The coating detaches and lifts from the substrate.

  • Recognition characteristics:
    • The coating detaches from the substrate partially or over an area.
  • Sources of error:
    • No adhesion primer was used. Most plastics require an auxiliary to allow coatings to adhere.
    • Plastic-Primer applied too thickly in the application. This material loses its ability to adhere to plastic substrates if the layer thickness is greater.
    • Additives for plastic substrates are not mixed into filler materials. Many base fillers have not been developed for the direct use of plastics. Here, either adhesion primers are needed as a base coat, or certain additives are added to the material.
    • Plastic substrates are not carefully cleaned or annealed, or the wrong cleaners are used. Plastics are cleaned with special plastic cleaners that do not attack plastics and have longer „open times“.
    • Plastics or fiber composite materials are not annealed before processing. In this process, residual release agents and solvents are transported to the surface. If annealing is not carried out, „smear layers“ can form between the coating and the object during the drying phase. Thus, the material loses its adhesion to the substrate.
    • Wrong material for the intended use (properties are not correct).
    • Flash-off times not observed. Too many solvents in the lower paint layers. If one of the upper „closes“, these diffuse between the layers and change the material properties and adhesion to the substrate.
    • Incorrect mixing ratio.
    • Material from third-party systems used. Some materials are more sensitive than others. Incompatibilities may occur.
    • Wet-on-wet filler systems should be allowed to flash off or dry through for too long. Applying material without intermediate sanding involves risks of the material flaking off.
    • The substrate has not been carefully sanded. Many materials used need a substrate that is sanded. Here, the adhesive property of the binder is not strong enough to hold on poorly or unsanded substrates.
    • Faulty material. Filler materials were processed too thickly. (These are the familiar images from relevant Instagram and YouTube channels when large filler plates peel off from the substrate).
    • Polyester filler or spray filler is applied on galvanized substrates without approval for zinc.
    • Drying with the IR heater was too close and/or too hot.
    • Moisture in the substrate.
  • Error prevention:
    • Check substrates for load-bearing capacity with the solvent test.
    • Flash-off times must be observed. In cold ambient temperatures, the drying process may have to be supported with IR.
    • After flash-off, topcoat basecoats with clearcoat in the correct time window (observe the manufacturer’s specifications in the technical information), thus ensuring the bonding of the materials.
    • Apply primer for the corresponding substrate. Not all materials have the property to adhere everywhere. Therefore, special attention must be paid here.
    • Do not just mist on clear and topcoats. The material must be able to adhere to the substrate through the binder and solvent.
    • Select a material for the right application. Here you need to consider the material properties.
    • Process materials according to the manufacturer’s instructions.
    • Carefully sand the substrates.
    • Prepare and anneal plastics correctly.
    • Keep an eye on ambient temperatures. The red line for temperatures is 20°C. At this temperature, all material properties have been tested in the laboratory. Anything below this does not meet the specifications. In practice, unfortunately, this point looks completely different, and you are on your own as a painter.
    • With most air-drying systems (poly aspartates) it is necessary to cure the basecoat. Here, proceed according to the technical information of the manufacturer.
  • Repair path:
    • Flaking coatings can only be repaired by completely removing the material, then insulating with a suitable filler and applying a new coat of paint.
    • On plastic parts, all the material must be removed down to the raw plastic. Without primer, the next stone chip will be your
    • Filler systems that have come loose must be sanded down to load-bearing surfaces and rebuilt throughout.
  • Notice:
    • Dried-through wet-on-wet systems: Imagine a glass plate on which a clear coat is applied. This is what happens when unsanded substrates or substrates that have been allowed to flash off too long are painted over. Adhesion is not possible there without assistance.
    • Some materials, so-called DTM products, would hold on to these substrates, provided the material properties allow it, on unsanded substrates.
    • Base coats, however, need a certain roughness in the sanding pattern and thoroughly prepared substrates with load-bearing material to anchor.