Liquid Coatings Troubleshooter - Application Issues

Liquid Coatings Troubleshooter - Application Issues

 

Slow Dry Time

  • Humid weather.
    • If possible, place in heated drying room.
  • Cold weather.
    • Maintain a temperature of at least 65°F. 76°F is desirable for normal drying.
  • Greasy, oily, or otherwise unclean paint surface.
    • Clean surface carefully with volatile solvents. If metal, use special metal treatments such as alkaline or acid cleaners and phosphatizers.
  • Failure to stir all pigment of pigmented finishes into proper suspension before application. Failure to stir properly unbalances the formula of applied material and often will cause poor drying.
    • Stir the material thoroughly so that liquids and pigment will be evenly dispersed.
  • Improper ventilation.
    • Provide ventilation and air movement.
  • An attempt to fill rough wood or metal by applying a heavy coat retards thorough drying.
    • Do not attempt to use finish coat as a surfacer. Apply only a full covering coat. Do not exceed recommended dry film thicknesses.
  • Improper catalyzation.
    • Follow instructions.

Poor Hiding

  • Over-reduction.
    • Add fresh, unreduced material to that which has been reduced.
  • Application on very hot, smooth surface which tends to cause film to flow off.
    • Use a faster evaporating solvent. Remove from direct sunlight.
  • Pigment not properly stirred into suspension.
    • Agitate thoroughly to properly distribute pigment.
  • Too-slow evaporating solvent, causing too much flow.
    • Use faster evaporating solvent.
  • Improper atomization.
    • Adjust spray equipment.
  • Low film thickness.
    • Apply more paint with more passes of spray gun. Use higher solids paint (less reduction), or faster thinner.
  • Lighter colors (lead- free yellows, oranges and reds).
    • Use a white primer to prevent shadows from showing through.

Lack of Flow (see Orange Peel)

  • Insufficient reduction.
    • Reduce or heat paint according to instructions.
  • Use of solvent with too fast evaporation rate.
    • If fast evaporation is due to local weather conditions, choose slower evaporating solvent than originally recommended.
    • Improper atomization of spray gun.
    • Adjust spray equipment.
  • Application of too thin a film.
    • Apply more material to surface.
  • Draft conditions.
    • Find reducing solvent or blend to provide proper flow in adraft or eliminate the draft.

Color Separation

  • Poor agitation.
    • Stir thoroughly to properly distribute pigment.
  • Too thick a film.
    • Reduce film thickness.
  • Too slow reduction solvent.
    • Use a faster solvent.

Dusting

  • Wrong solvent blend.
    • Usual remedy is to choose a slower evaporating thinner.
  • Excess spray pressure.
    • Reduce pressure.
  • Over-reduction of material.
    • Use less reduction. Add fresh material to that which has already been over-reduced.
  • Gun held too far from surface.
    • Hold gun at proper distance from work (usually 8 –12 inches).

Sagging

  • Sagging can be caused by either over-reduction or by use of too slow a solvent.
    • Use the proper solvent consistent with the general nature and temperature of the surface to be coated.
  • Application of too heavy a coat.
    • Do not apply so much material to the surface.
  • Draft conditions.
    • Eliminate draft.
  • Strong sunlight causing top drying and consequent later slippage
    and wrinkling of film on vertical surfaces.
    • Avoid application in strong sunlight.
  • Uneven distribution of spray coating.
    • More careful application by proper handling of spray gun.
  • Jerky operation of mechanical equipment for withdrawal from dip tank.
    • Repair or redesign equipment.
  • Cold weather.
    • Use faster evaporating reducing thinner or bring room temperature up to 75°F.

Bleeding

  • Organic red pigments or various dyes used in undercoats have not been sealed properly. This causes a pink or reddish shade to show through a white topcoat.
    • Best remedy is to avoid use of bleeding colors (usually redsor oranges). Where bleeding colors have been used, a weak solvent or water base sealer usually will seal the bleeding.

Orange Peel (see Lack of Flow)

  • Use of improper solvent for prevailing temperature condition.
    • Choose a solvent which will allow greater flow.
  • Improper handling of spray equipment.
    • Adjust air pressure and fluid flow, and be sure that gun isheld at proper distance from work.
  • Application of too thin a film, not allowing proper flow.
    • Apply heavier coating.

Lifting or Wrinkling

  • Sometimes strong solvents tend to react with preceding coat.
    • Be sure that the undercoats are thoroughly dry. Use primer recommended. Use thinner with lowest solvent strength which will still act as steady diluent.

Poor Electrostatic Wrap

  • Dry over spray.
    • Use retarder such as 150 reducer. Reduce pressures.
  • Low polarity.
    • See paint and equipment manufacturer's recommendationsfor reduction of paint and polarity requirements.
  • Electrical.
    • Check power at transformer and gun.

Bubbling/Pin Holes

  • Drafts which cause surface drying and force the solvent to break
    through surface film in order to evaporate.
    • Avoid excessive drafts or sunlight.
  • Fine drops of moisture coming through separator in spray apparatus.
    • Clean spraying equipment.
  • Air entrapment.
    • When using air assist airless equipment, lower the atomizing air and raise the fluid pressure. Try a smaller tip orifice size.
  • Thinner evaporates too fast.
    • Use slower thinner or lower viscosity.
  • Spots of grease on surface.
    • Clean surface carefully.
  • Material applied while frothy, following violent agitation.
    • Allow froth and bubbles to subside before applying.
  • Poor wetting of the surface by the enamel.
    • Wipe surface to be sprayed with a solvent-saturated clothbefore application of the next coat.
  • Bake oven is too hot.
    • Allow more flash off time or lower temps.

Washing of Film

  • In some dip operations, faulty ventilation in the hood above the dip tank allows a concentrated collection of solvent vapors. This reduces the film on the object which has just been withdrawn from the dip tank, thereby causing the film to wash or flow off the finishing surface.
    • Provide proper ventilation over dip tank or in spray booths.
  • Faulty ventilation in oven causes concentration of vapor.
    • Provide proper ventilation.
  • Wash caused by cleaning solvents remaining in crevices.
    • Be sure surface is clean and dry, as well as all crevices.Change angle of drain.

Fish Eyes

  • Silicone contamination.
    • Locate source of contamination and eliminate it. Check wipers, belt dressings, lubricating greases, and oils, hand creams, metal and wood polishes, etc., as possible sources.
  • Oil or water in air lines.
    • Provide adequate filtration.