Changing the colour of the coat due to a chemical reaction (peroxide harder in polyester putty with topcoat).
- wrong proportions of hardener in polyester putty,
- lack of sufficient insulation of polyester materials,
- remains of tar and bituminous masses.
- use appropriate proportions of hardener in polyester putty,
- recommended insulation of polyester materials with epoxy primer,
- before coating, remove the residues of bituminous masses and tar.