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Technical Support Training

Frequently Asked Questions and Answers

BEST PRACTICES AND PAINT FILM DEFECTS


MIXING


  • PAINT SHOULD IDEALLY BE STORED BETWEEN 18°C AND 23°C
  • THOROUGHLY CHECK ALL TINS IN ORDER TO DETECT ANY DAMAGE OR LEAK DURING THE TRANSPORT
  • TURN DOWN THE DRUMS
  • CHECK THE MATERIAL IS STILL IN SHELF LIFE BEFORE PROCEEDING
THOROUGHLY CHECK THE ACTIVATOR :
A SWOLLEN DRUM COULD REVEAL HUMIDITY CONTAMINATION THAT COULD CAUSE A DANGEROUS GAS ESCAPE : CONTAINERS SHOULD BE OPENED CAREFULLY
IF GELLED PARTICULES OR MILKY AREAS APPEAR, THIS ALSO SUGGESTS A HUMIDITY CONTAMINATION
CONTAINERS SHOWING EITHER OF THESE EFFECTS SHOULD BE DISCARDED AND NOT USED
  • CHECK THAT ANY VESSEL THAT THE PAINT IS TRANSFERRED TO
    IS CLEAN AND FREE OF ANY CONTAMINATION
  • BEFORE PAINT PREPARATION, ESPECIALLY THE PRIMERS, IT
    IS RECOMMENDED TO CHECK MECHANICALLY THE PRODUCTS
    THE BEST MIXING WAY IS TO USE A PAINT SHAKER « RED DEVIL »
  • OPEN THE TINS CAREFULLY
  • MAKE SURE THERE IS NO DEPOSIT ON
    THE BASE OF THE TIN
  • CHECK THE COLOUR HOMOGENEITY

ADD THE HARDENER (ACTIVATOR) TO THE BASE SLOWLY UNDER SLOW AGITATION. THE HARDENER MUST BE ADDED TO THE BASE AND NOT THE REVERSE. ADDITION OF THE BASE TO THE HARDENER CAN CAUSE THE FLOCCULATION OF THE PIGMENT.
MIXING INSTRUCTIONS ARE PROVIDED ON TECHNICAL DATA SHEET AND ON THE BASE LABELLING.
ANY DEVIATION CAN RESULT IN THE LOSS OF THE PHYSICAL PROPERTIES OF THE COATING

  • ADHESION
  • GLOSS
  • APPEARANCE
  • COVERING POWER
  • DURABILITY
  • DRYING
  • CHEMICAL RESISTANCE
  • POT LIFE

ADJUST THE VISCOSITY OF THE MIXING AS RECOMMENDED IN THE TECHNICAL DATA SHEET OR IN THE MANUFACTURE PROCEDURES.
ADD THE THINNER UNTIL THE CORRECT VISCOSITY IS ACHIEVED.
A BAD VISCOSITY CAN RESULT IN :
ORANGE PEEL SAGGING RUNS
DRY SPRAY POOR OPACITY
REDUCE POT LIFE CHANGE IN GLOSS
MICRO-BLISTERING WETTABILITY, WET-EDGE TIME,
DRYING TIME


APPLIED FILM

THE PRODUCTS SHOULD BE APPLIED RELATIVE TO STRICT APPLICATION SPECIFICATIONS. ANY DEVIATION IN THE INSTRUCTIONS CAN RESULT IN PROBLEMS SUCH AS.\

OVER THE FILM
ADHESION FAILURE BETWEEN COAT (FAILURE IN APPLICATION PROCEDURES)
EXCESSIVE WEIGHT OVER THE AIRCRAFT (THICKNESS TOO IMPORTANT)
POOR APPEARANCE (INADEQUATE THINNING)
SLOW CURE (INADEQUATE MIXING RATIO T°c <15°c)
MICRO-BLISTERING (TOO IMPORTANT THICKNESS, T°c > 30°c, POT LIFE OUT)
CHANGE IN GLOSS (DRY SPRAY, ORANGE PEEL)
ORANGE PEEL (INADEQUATE SPRAYING EQUIPMENT (NOZZLE, CAP, BAD THINNING)
CRACKING (LAST COAT CURED BEFORE THE 1ST)

OVER THE PROPERTIES OF THE FILM
POOR RESISTANCE TO CORROSION (INADEQUATE SURFACE PREPARATION, TOO LOW THICKNESS, SPECIFICATIONS RELATIVE TO THE SCHEMES HOT FOLLOWED)
POOR CHEMICAL RESISTANCE
POOR SURFACE APPEARANCE
EROSION PROBLEMS


Striping

Appearance:A light and dark striped effect usually running parallel, showing up in finished work, especially in metallics and pearls.

Cause
Heavy application on the outer edges of a spray fan and little or no paint in the centre of the fan. Excessive air pressure, ‘splitting’ the fan (dirty air cap).
Uneven overlapping of the spray gun stroke.

Prevention and Cure
Use materials at recommended thinning, air pressures and/or reduce fan width.
Take care in overlapping each stroke by 50% over the preceding coat.
Hold gun at an even distance to the job at all times.
If striping has occurred, recoat with a double coat using recommended thinner ratios and specified pressures and apply correct gun technique.


Blistering (from Contamination)

Appearance:Irregular pattern of blisters appearing in the dried paint finish.

Cause
Improper substrate cleaning or preparation.
Contamination (air lines, shop tools, old finish or previous repair).

Prevention and Cure
Clean all surfaces to be painted and remove grease, wax, polish etc.
Ensure compressors and air lines are drained regularly and kept clean at all times.
If blistering has occurred, sand affected area to a sound surface and refinish. In extreme cases, remove finish down to the metal and refinish.


Dirt in Paint

Appearance:Inclusion of dirt or dust in the finish.

Cause
Applying finish over dirty and dusty surface.
Failure to strain all materials before use.
Airborne dust, contamination of paint during spraying.

Prevention and Cure
Blow off the job with compressed air and wipe over with a tac rag before spraying.
Stir all materials thoroughly to obtain a uniform mixture and strain before use.
Clean the surrounding work or booth area before spraying. If already occurred, sand down to a smooth surface and refinish. If isolated dirt, sand flat with fine paper, compound and polish.


Fish Eyes

Appearance:Small saucer shaped imperfections appearing in the top coat. Sometimes they appear in isolation, at other times in 'clusters'.

Cause
Surface contamination, oil, silicone polish residual etc.

Prevention and Cure
Ensure all surfaces are thoroughly cleaned before any operation. (Use a solvent based water-miscible cleaner or mild detergent. In severe cases, use water-miscible cleaner in flatting water).
Ensure that any operations involving the use of silicone products are carried out in a building separate from the paint shop.
Remove the affected paint and respray.

NOTES
A) Use a recommended mineral oil for lubrication of the compressor.
B) Be sure that oil and fluid hoses are suitable. Silicone contamination has been traced to hoses not specially manufactured for spray painting.
C) The use of silicone-containing additives to prevent cratering is not recommended. These additives contaminate the paint shop and other work around and can also lead to future adhesion failure.


Mottling

Appearance:
A flooded, heavy hammer-like effect in metallic or pearl finishes. Gives the appearance of small dark circles surrounding a light metallic centre or patches of light and dark areas of colour.
In basecoats, the effect is often not apparent until application of the clearcoat.

Cause
Incorrect reduction in thinner, usually underthinning.
Holding the gun too close to the job.
'Piling-on' in heavy coats causing the aluminium particles to flood.
Shop temperature too cold.
Insufficient time between coats.
Poor application technique.
In basecoats, insufficient flash-off times before application of clearcoat. Dry spray on surface of basecoats prior to overcoating with clearcoat.

Prevention and Cure
Use thinning ratio recommended.
Use correct spray technique for gun distance and speed.
Do not pile-on in heavy wet coats.
Warm shop conditions if possible.
Follow flash off times between coats as recommended.
If mottling has occurred, allow colour coat to set up, then apply another double coat using correct thinning ratio and spray technique. (Cross coating recommended.)
If mottling occurs in basecoats after application of clearcoat follow paint manufacturer's recommendation for paint type.


Orange Peel

Appearance:The pock-marked or lumpy appearance of a sprayed film due to its failure to flow to a level film.

Cause
Material too thick
Too high temperature
Poor quality thinner or insufficiently thinned or wrong grade of thinner.
Improper atomization caused by faulty handling or setting of the spray gun.
Prevention and Cure.
Choose correct grade of thinner and thin according to directions.
To avoid poor spraying technique, use arm in full, long strokes, keeping parallel to the surface without wrist action. Hold gun at right angles 15-20 cm for lacquers and 20-25 cm for enamels from the surface, using specified air pressures. Use suitable gun set up for topcoat being used.
Do not fan air over surface as this causes surface drying without flow 。
To remove orange peel effect, buff with a suitable compound when thoroughly dry.
In extreme cases fine sand down to a smooth surface and rebuff, or refinish, using a grade of thinner suitable for the spraying conditions.


Overspray

Appearance:Dusty appearance on finish giving either a fine or coarse, grainy or sandy effect.

Cause
Usually found where the finish forms a center line on bonnets, turrets or overlaps and join up areas on large spray jobs.
Excessive air pressure, poor (especially hot) air movement around the job or thinner being too fast, or by improper use of the spray gun.

Prevention and Cure
Use good spraying technique.
Use good quality thinner.
Use correct air pressure.
This to correct viscosity.
Add retarder if conditions are hot and dry, or use slower thinner.
Use correct spray gun set-up.
Avoid turbulent air movement.
Undercoats : Remove by washing off with thinner and rag, or allow to harden and remove by flatting.
Finishes: Dry spray of the final coat may be removed by flatting with P1200 grade abrasive paper, and the gloss restored by using a polishing compound.


Peeling

Appearance:Evident as peeling or easy removal of the finish.

Cause
Improper substrate cleaning or preparation.
Contamination (air lines or from the original finish etc.)
Wrong choice of undercoat for particular substrate e.g. aluminium, zinc coated metals or plastics.
Incompatible layers of paint.

Prevention and Cure
Clean all surfaces to be painted to remove wax, grease, polish and other foreign materials, before any sanding and again before any spraying. Sand thoroughly to provide sufficient 'key'. Use metal conditioners where specified.
Use only undercoats recommended for the particular substrate and top coat finish being used.
Use only recommended cleaners and primers for plastic substrates.
If peeling has taken place remove the finish for an area considerably larger than the affected area to a sound base and refinish.

Pinholing

Appearance:Characterised by the appearance of minute holes on the surface of the film.

Cause
Material air flashed too long prior to baking.
Wrong reduction of thinner (amount or grade).
Improper substrate cleaning and preparation.
Moisture in spray lines.
'Piling-on' in heavy wet coats, trapping in solvents.
Poor shop temperature (too hot or cold).
Effect of old finish or previous repair, existing pinholes unnoticed.
Improper dry caused by fanning with air.
Insufficient atomization or breaking up of materials.

Prevention and Cure
Follow any baking schedule closely
Choose correct thinner and reduce as recommended.
Clean all surfaces to be painted to remove wax/grease/polish and other foreign materials, before and after initial sanding.
The drain valve of the air compressor should be opened daily to allow drainage of collected materials.
Do not apply materials too heavily, apply in medium coats to allow proper evaporation of solvents.
Do not fan surface with air as this causes skinning of the surface and traps solvents in the film.
Ensure material is atomized sufficiently by correct gun and pressure adjustments.
If pinholing has occurred, sand down to a sound surface and refinish.

Poor Hiding

Appearance:The inability of a pigmented or coloured finish to completely hide the colour of the substrate.

Cause
Settling of pigmented finishes, usually after thinning, and not stirred, will cause too much resin being applied with the pigment left in the bottom of the container.
Faulty spraying technique i.e. not over-lapping by 50% each succeeding stroke, will result in banding and poor overall coverage.
Over-thinning of lacquers or enamels may result in too thin a film being applied.

Prevention and Cure
Stir all materials thoroughly to obtain a uniform mixture.
Use correct spraying technique i.e. overlapping each stroke by 50% over preceding coat, and holding the gun at right angles to the job at all times.
Follow recommended thinning ratio at all times.
If poor hiding has taken place, refinish again using correct thinning ratio and spraying
techniques and apply sufficient paint.

Runs or Sags

Appearance:Apparent as a running, sagging finish, resulting from too much material in the area.

Cause
Too much thinner.
Too heavy coats.
Too wet coats.
Short flash-time between coats.
Cold shop temperatures.
Wrong gun techniques.

Prevention and Cure
Reduce material according to TDS directions.
Apply medium coats only
Regulate fluid adjustment on spray gun to cut down flow of material.
Increase flash-time between coats.
Allow for temperature conditions during application.
Don't hold gun too close. Move at a uniform speed at right angles to the surface.
If runs or sags have already occurred, sand down to smooth surface and refinish. In some cases, it may be possible to carefully block wet sand out the run with Microfine paper then compound and polish.

Floating and flooding

Causes
Formulation
Too wet film
Material ( base ) not well dispersed
Gun set up

Preventions and cure
Reduce the amount of paint applied
Extend the drying period between coat
Check spray gun set up
Agitate the mixing during the application