Bleeding

Patchy bleed-through from the substrate, which may be reflected as a partial spot or with a coloration of the topcoat.

• Sources of defects:
  • Over-curing of polyester materials such as putty products – peroxide from the hardener can react with other substances.
    In these cases, the excess hardener is distinguished by reddish-brown spots.
  • Colorants from the old coating are carried to the surface by solvents.
  • Unremoved tar or bitumen residues from highway construction sites – recognizable by small, brown, or dark yellow spots.
  • No or insufficient barrier layer over polyester materials.
  • The filler was painted over after too short a drying time.
  • Markings made by ballpoint pen refills or permanent markers containing solvents can also penetrate the coating. Do not mark directly on coatings, despite good cleaning it can happen that markings or written become visible!
  • Polyester materials have been coated without a barrier layer.
  • Visible color change or „bleeding in“ of the upper coating layer due to absorption of color pigments from the substrate material.
• Error prevention:
  • Adhere precisely to mixing ratios.
  • Test old coatings for load-bearing capacity and solvent sensitivity (solvent test).
  • Carefully clean the object before applying the material – remove all impurities.
  • Make markings on previously applied adhesive tape.
  • Apply multiple coats with sufficient flash-off and drying times.
  • Seal polyester substrates with suitable materials such as primers or fillers before coating.
• Repair route:
  • In most cases, only a new coating build-up with suitable materials can be carried out.

Example:
An object is painted with colored 2K 1-coat material and covered with clear coat,

The coating of the 2K 1-layer material was finished and the following clear coat was sprayed into the still „wet“ colored material. Thus, components of the colored 2K material are „stirred up“ and, under certain circumstances, shifted into the clearcoat layer. In this way, visible „bleeding“ can occur due to coating defects.