Discolouration

Cause

• Bad preparation of the surface to repair
• Remains of grease from bituminous mass
• Wrong hardener’s ratio of polyester putty

Countermeasure

• Before repairing, neatly remove grease
• Isolate the repaired surface with the primer e.g. epoxy in thin layers
• Remove old and damaged layers up to bare steel
• Use correct ratio of a hardener for polyester putties

Removal

• Sand, isolate and varnish again