A soft or muddy underground layer in multi-layer coatings
- Sources of error:
- The material used is set too short.
- The coating is too thick.
- Base coats in multi-layer build-up are not activated or cured according to the manufacturer’s specifications.
- The mixing ratio is not maintained according to technical information.
- The ambient temperature is too warm.
- Adjustment additives and hardener not adapted to temperature.
- Flash-off times not observed. Residual solvents remain in the substrate. The upper layer „closes“ and the material below remains soft.
- Impatience or deadline pressure.
- Error prevention:
- Adhere to mixing ratio according to technical information.
- Uniform paint application with sufficient intermediate flash-off time.
- Adapt hardener and thinner to ambient temperature. In summer, use long material.
- Painting in multi-layer build-up or difficult coatings, in general, should always be carried out in peace and quiet. Stress also causes coating defects.
- Repair path:
- The only way to repair this type of damage is to remove the entire material down to a load-bearing substrate. Re-insulate and renew the paint structure. Possibilities of material removal are washing off with solvent (nitro) or sanding. From practice, both are carried out and require quite a while until all residues are removed.
- When using solvents, however, it must be ensured that all other paint layers or fillers in the substrate are thoroughly dry and no 1K products were used (e.g. NC filler, spray can material uncured). These are then attacked by penetrating solvents.
- What happens in this process?
A number of parameters come together here.- If, for example, the ambient heat is high and a short curing agent is used, the surface „closes up“ and starts to crosslink before solvents have completely left the coating. This means that the remaining solvents or thinners are trapped. This means that the remaining solvents or aqueous additives can no longer escape from the substrate. The coating layer has no possibility to dry properly. Residual solvents then migrate back and forth between the „dried“ surface and the substrate, causing the material to soften.
Such paint damage can also be seen on screwed connections of materials that have not dried completely. The paint „turns up“ under nuts.
- If, for example, the ambient heat is high and a short curing agent is used, the surface „closes up“ and starts to crosslink before solvents have completely left the coating. This means that the remaining solvents or thinners are trapped. This means that the remaining solvents or aqueous additives can no longer escape from the substrate. The coating layer has no possibility to dry properly. Residual solvents then migrate back and forth between the „dried“ surface and the substrate, causing the material to soften.
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