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Coating defects

Blisters

Causes:
  • Too short flash off times between the coats
  • Too thick primer coat
  • Water polluted compressed air
  • Too high air humidity (over 80 % at 2k materials)
  • Condensed water due to temperature fluctuations in the compressed air installation 
Prevention:
  • Flash off between coats min. 5 -10 min/20 °c, or until surface is mark free
  • Compressed air should be dry and clean
  • Avoid the formation of condensed water in the air installation. Keep a stable temperature and humidity

Traces of sanding in a top coat

Causes:  
  • Sanding of the primer with unsuitable (too rough) abrasive paper
  • Sanding with unsuitable (too rough) abrasive paper of the substrate
  • Insufficient putty isolation prior to application of the top coat
  • Too low viscosity of top coat
Prevention:
  • Use abrasive paper of prescribed grit
  • Sanding marks with a fine abrasive paper
  • Isolate thoroughly puttied repairs with filler
  • Follow the prescribed viscosities of top coats
  • Follow the prescribed drying times
  • Follow the prescribed coating thickness

Bad adhesion to the surface

Causes:
  • Poorly prepared, contaminated surface (grease traces, finger prints, dust etc.)
  • Use of the materials, which are not suitable for certain types of substrates
  • thinning of material with unsuitable (not original) thinner
Prevention:
  • Clean surface thoroughly before painting
  • Always check which material is suitable to a certain type of substrate
  • Use of recommended thinners

Surface soaking

Causes:
  • Not dried through, not cure old coat
  • Too high thickness of old coating
Prevention:
  • Follow the prescribed drying times
  • Follow drying through times with synthetic (KH) coats
  • Isolation of problematic surfaces
  • Follow the prescribed thickness for coats

Sagging

Causes:
  • Incorrect material viscosity 
  • Too high film thickness 
  • Unsuitable spray gun (nozzle), pressure
  • Too cold material or substrate or too low room temperature
  • Use of unsuitable thinner
Prevention:
  • Follow technical instructions for use
  • Use a suitable spray gun
  • Warm the object and material to room temperature +20°C
  • Use of a recommended thinner

Craters

Causes:
  • Wax, grease, silicone contaminated surface
  • Compressed air contaminated through condensed water or oil residue
  • Use of silicone, polishing agents or sprays in the vicinity of painting area
  • Insufficiently cleaned surface before coating
Prevention:
  • Before coating clean the surface thoroughly with Ant silicone cleaner 
  • Regular maintenance of oil and water separators (filters)

Matt effect (gloss decrease)

Causes:
  • Too high air humidity
  • Surface soaking
  • Hardener defects – hardener reacted with air humidity
  • Humidity in compressed air supply
Prevention:
  • Follow technical instructions for the application of material
  • Keep hardener cans sealed properly
  • Enable sufficient air flow (during drying)
  • Follow drying times
  • Use the recommended hardener

Bad levelling

Reasons:
  • Unsuitable (too high) viscosity
  • Unsuitable application technique
  • Unsuitable working temperature
  • Use of unsuitable thinner
  • Unsuitable spray gun (nozzle), pressure
Prevention:
  • Follow technical instructions for use – viscosity and temperature
  • Use of prescribed spray gun (nozzle)
  • Use of prescribed thinner
Repair of incurred damage:
  • Sand to filler and repeat painting of top coat as prescribed

Popping

Reasons:
  • Incorrectly dried-through filler
  • trapping of solvents and air because of too high film thickness
  • No flash off between coats
  • Wrong hardener and thinner
  • interrupted drying (not following drying time)
Prevention:
  • apply the prescribed coat thickness
  • wait between the first and the second coat 10 – 15 min. /20 °C or until mark-free surface
  • Regular check of activation and temperature of a drier
  • follow prescribed flash off times between coats and final flash off
  • use the prescribed hardener and thinner.
Repair of incurred damage:
  • Sand to sheet metal and repeat painting of top coat

Sandy surface

Reasons:
  • Isocyanate hardener for 2K materials reacted with air humidity
Prevention:
  • After opening the packaging with isocyanate hardener, use it up as soon as possible or
  • Close well
  • Before repeated use of hardener from the already opened packaging: check hardener, which should be clear, colourless and without any floating particles
Repair of incurred damage:
  • Sand to filler and repeat painting of top coat

Incompatibility of the materials

Reasons:
  • Mixing of enamels produced with different binders (resins), which are incompatible or only partially compatible. Example: MOBIHEL Enamel and MOBIHEL 2K acrylic enamel (defect size depends on ratio of different materials)
Prevention:
  • Follow instructions for product use
  • Mix only mixing enamels from the same quality series of MIX-es
Repair of incurred damage:
  • Sand to filler and repeat painting of top coat

Cloudiness in two-coat metallic coats

Reasons:
  • Unsuitable application technique (nozzle, pressure)
  • Too wet base; not thoroughly enough mixed base before use
  • Use of inappropriate thinner
  • The coated surface has unsuitable temperature (too cold, too warm)
Prevention:
  • Use the prescribed application technique
  • Mix the base thorouggghly prior to use
  • Use prescribed thinner
  • Ensure suitable temperature of the surface to be coated 

Traces of water drops

Causes:
  • Too short drying time
  • Too thick coat
  • Too short flash-off time between individual coats
Prevention:
  • Follow technical instructions relating to the drying times
  • Follow instructions for application method
  • follow flash-off times between individual coats

Holes

Causes:
  • Not enough dried through surface
  • Not isolated polyester materials
  • Pores were not polished
Prevention:
  • Thorough drying of preceeding materials
  • Pores should be thoroughly polished or putty applied
  • PE putty should always be isolated with primer before application of top coat

Spots of bleaching of the top coat

Reasons: 
  • Too much hardener in PE putty
  • Poorly mixed hardener in the PE putty 
Prevention: 
  • Check addition of a hardner
  • Mix thoroughly
Repair of the incurred defect: 
  • Sand back to bare metal and repeat puttying according to instructions