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Tools and Equipment for Paint Repairs > < Factory Paint Application
Paint - General Information - Paintwork Defects and Damage Focus 2004.75 (07/2004-)
Description and Operation

Diagnosis and Damage Assessment

Paint concerns, regardless of their causes, are part of the everyday work in the paint shop. Correct damage assessment and determination of the cause are preconditions for a professional resolution of a paint concern.

Paint concerns can still occur through a variety of causes, despite improved paint materials and new spray methods.

NOTE:
NOTE:A first appraisal of the paint damage should be done before cleaning. External factors such as rust, droppings, incorrect or insufficient paint care can then be more easily detected.

Diagnosis is best done in daylight but not in direct sunlight. Exact evaluation can also be done under artificial light from special luminescent lamps.

Paint damage guide

    The most important paint damage concerns which make a paint repair necessary are:

  • Damage from biological paint contamination such as bird or insect droppings, tree resin and aphids.
  • Chemical paint damage caused by industrial contaminants such as smoke, fuel, acids, oils.
  • Mechanical damage caused by stone impact during operation, scratches in the car wash and parking.
  • Damage caused by faults in treatment. Application defects such as paint runs or orange peel.
  • Dirt inclusions in the paint layer, e.g. caused by dust in top coat or textile lint.
  • Damage due to corrosion.

Before repair of such paint concerns, exact diagnosis must be performed to determine the cause exactly. On the spot diagnoses using simple aids and processes are often enough.

    Diagnosis without disturbing the paint is done by:

  • Optical inspection without visual aids, under suitable light conditions from a suitable angle and correct distance.
  • Optical inspection with the help of a magnifying glass.
  • pH paper.
  • Measurement of the thickness using FE / NFE coating thickness meters for ferrous (FE) and non-ferrous metals and non-magnetic steel (NFE) - magnetic process on steel panels, eddy current process on non-metals.

A test method where the traces of testing can be easily removed again is the finger nail test. With suitable experience the existing hardness of the paint can be determined.

    Test methods where the paint is partially destroyed are:

  • Pencil hardness test.
  • Adhesion test using adhesive tape.
  • Lattice cut test process to check the strength of adhesion.

Under certain circumstances these test methods are not enough for a certain diagnosis. In this case, paint diagnosis under laboratory conditions must be performed.

Measuring and testing equipment for painted surfaces

Coating thickness measuring devices

Magnifying glass

pH paper (together with water)

Suitable photographic equipment with macro lens

Shine measuring equipment

Paint damage caused by environmental factors

  • Bee droppings
  • Bird droppings
  • Insects
  • Tree resin and sap
  • Aphid secretions
  • Tar spots
  • Cement, plaster and slaked lime
  • Rust film/deposits from industrial fallout
  • Battery acid
  • Brake fluid

In all the cases of paint damage described below, if the damage is irreversible a new paint finish must be applied.

Paint damage cause by bee droppings

Bee droppings can be recognized on a paint surface through its yellow or brown color and sausage or drop-like shape with a diameter of 3-4 mm.

    Cause/damage pattern:

  • In combination with heat and high air humidity, bee droppings leave discolorations and cause paint decomposition.
  • The paint can be destroyed down to the filler.

    Repair of damage:

  • If the damage is light, perform a polishing repair.

Paint damage caused by bird droppings

Bird dropping damage appears most often as matt, etched topcoat areas of various sizes. If left on the vehicle for a long time, crack formation and etching down to the filler will occur.

    Cause/damage pattern:

  • Bird droppings are particularly harmful in combination with heat and moisture. The urea (white part) has a very high salt content and is very aggressive.
  • The intensity of the damage varies depending on the type, quantity, contact time and extent.
  • Cracks, etching, marks up to dissolution of the top coat are the results.

    Repair of damage:

  • If the damage is light, perform a polishing repair.

Paint damage caused by insects

At insect impact locations on the hood, roof and bumper, small etched or etched through paint marks with partially visible spots of filler.

    Cause/damage pattern:

  • The top coat layer is destroyed in a short time by surface swelling and etching.
  • Colliding insects stick to the paint surface. In combination with moisture and heat, because of the resulting acids the insect bodies sink into the paint top coat.
  • The corrosion is G, C, U or O shaped and is only a few millimeters thick.

    Repair of damage:

  • Wash the vehicle, treat the affected area with insect remover. Clean the paint surface several times.
  • Protect with hard wax.

Paint damage caused by tree resin or sap

Small yellow-brown marks or drops on the horizontal parts of the vehicle. The drops melt in sunlight. Resin damage only occurs in the warm summer months.

    Cause/damage pattern:

  • Because of their chemical composition, tree resins combine with or adhere very well to paint top coats and cause them to swell. The higher the temperature, the more intensive is the chemical bonding between the resin and the paint topcoat surface.

    Repair of damage:

  • Soak several times using a cloth saturated with a petrol & paraffin mixture.
NOTE:
NOTE:After successful cleaning the top coat must be preserved.
  • Swellings can be removed by warming.

Paint damage from aphid secretions

Small, round, matt marks about 1 mm diameter and etching with small islands down to the filler. Fresh aphid excrement looks like small drops of honey.

    Cause/damage pattern:

  • Aphids produce a mixture of starch, leaf acid and sugar from sap in leaves. Under the effects of warming and moisture this can turn into alcohol.
  • The round shape of the damage and the island of intact paint are typical.

    Repair of damage:

  • Remove the excrement as soon as possible.
  • Small single matt locations without etching can be repaired using a polishing repair.

Paint damage caused by tar spots

Yellow or dark marks.

    Cause/damage pattern:

  • Firmly stuck spots of tar which lead to discoloration of the surface. In some cases penetration through the clear lacquer into the top coat.

    Repair of damage:

  • Clean the paint surface with tar remover and polish.

Paint damage caused by cement, plaster and slaked lime

Damage appears as whitish matt marks on the top coat.

    Cause/damage pattern:

  • Corrosive alkaline compounds interacting with moisture.

    Repair of damage:

  • Wash immediately if the contamination is fresh.
  • If the contamination has dried on, dissolve and neutralise it with vinegar, then thoroughly wash off with water and rinse.
  • Rectify mild damage using a polishing repair.

Rust film/deposits from industrial fallout

Small round marks, about 1 mm in size, in all shades from black, grey, blue to reddish, on the horizontal surfaces of the vehicle.

    Cause/damage pattern:

  • Deposits from oil fired systems and industrial plant, especially at high humidities and inversion weather conditions, cause damage to the paint top coat.
  • As the activity time increases so called rust halos form. They spread as long as the deposits corrode.
  • Industrial fallout containing iron will no longer be removable after a few days!

    Repair of damage:

  • Remove the dust using an industrial fallout remover and thoroughly wash.
  • Polish the paint surface.
NOTE:
NOTE:Never try to remove the particles of industrial fallout by polishing or rubbing!
  • Use cleaning dough.

Damage caused by battery acid.

Splashes of battery acid caused by carelessly topping up the battery.

WARNING:
WARNING:Batteries contain sulphuric acid. When working near the battery, or where there is battery acid on the vehicle body, protect the skin and eyes from contact with the acid. If battery acid contacts the skin or enters the eyes, flush the affected area immediately with water (flush for at least 15 minutes) and call a doctor without delay. If acid is swallowed, call a doctor immediately. Failure to follow these instructions may result in personal injury.
NOTE:
NOTE:High temperatures accelerate the attack on the top coat. At 50°C the top coat layer breaks down after about 15 minutes!

    Cause/damage pattern:

  • Etching of the paint layer to decomposition of the paint finish.

    Repair of damage:

  • Flush the acid splashes with plenty of water and neutralize with car washing liquid.
  • If the contact time of the acid was short, perform a polishing repair.

Paint damage caused by brake fluid.

Careless handling of brake fluid. The glycols contained in the fluid cause swellings.

    Cause/damage pattern:

  • The temperature and contact time are critical. Splashes lead to loss of shine and lightening of color.

    Repair of damage:

  • Flush immediately with plenty of water.
  • The swellings can often be made to recede completely by treatment with the radiant heater or in the paint drying oven at max. 60°C for about 1 hour.

Mechanical damage

Stone impact damage or mechanical damage

Mechanical damage caused by impact of stones or other hard objects and extending down to the metal panel lead very quickly to corrosion and rusting under the paint on the adjoining surface.

    Cause/damage pattern:

  • Paint damage caused from the outside, down to filler, primer or metal panel.

    Repair of damage:

  • Sand or blast out.
  • Use anti-corrosion primer.
  • Apply top coat.

Damage due to corrosion

Blistering/rusting below

Air or water filled blister-shaped raised areas in the paint film.

    Cause/damage pattern:

  • Overpainting corroded steel panel.
  • Condensation in the spray air.
  • Sanding water not dried out or salt crystal residues.
  • Road chippings and road winter grit containing salt.

    Repair of damage:

  • Sand the affected area of damage or the body component and re-create the paint finish.
  • More severe and larger areas of rusting below must be repaired using the corresponding repair painting, Repair Level III or IV.

Damage caused by faults in treatment

  • Craters
  • Paint boils
  • Adhesion defects
  • Adhesion defects - clear lacquer
  • Sanding scores
  • Formation of stripes
  • Peeling/blistering on plastic parts
  • Blistering on polyester material
  • Peroxide marks in metallic paints
  • Crack formation
  • Shrinking back/zone edge marks
  • Blistering
  • Etching
  • Paint wrinkles/puckering
  • Cloud formation
  • Spots/metallics
  • Metamerism/color deviations
  • Washing out
  • Loss of gloss
  • Covering ability/areas of thin paint
  • Flow problems/orange peel
  • Dirt embedded in metallic base paint
  • Dirt embedded in top coat
  • Water marks
  • Paint runs
  • Swirl marks

Craters

Crater-like single or extensively occurring depressions with raised edges, in top coat or the intermediate layers.

    Cause/damage pattern:

  • Substrate not adequately cleaned with silicone remover.
  • Spray air contaminated by oil residues and water accumulations.
  • Filter ceiling not adequate for requirements.
  • Use of polishes, cleaning agents or sprays (e.g. interior sprays) containing silicone.
  • Oil, wax, grease, silicone containing residues.
  • Working clothes contaminated by materials containing silicone.

    Repair of damage:

  • Sand paint surface, clean with silicone remover and apply one thin spray pass. Let it begin to dry well, then apply several thin and dry sprayed passes.

Paint boils

Small, hard, closed or burst blisters in the paint top coat. They appear locally in groups or spread individually across the whole surface. Sanding opens up a larger cavity, under which the primer can often be seen.

    Cause/damage pattern:

  • Paint applied in layers which were too thick.
  • Specified flash-off and drying times between coats were not adhered to.
  • Specified working viscosity and spray pressure were not adhered to.
  • Use of unsuitable hardener and thinner materials. (Solvent combinations in paint system not optimally matched).
  • Poor booth conditions.

    Repair of damage:

  • Single boil blisters can be removed using polishing.
  • After thorough drying, sand the top coat at the affected areas, clean with silicone remover and re-paint. Fill any fine pores still present with 2-component acrylic filler.
  • On larger areas of damaged topcoat, sand completely away and apply new paint finish.

Adhesion defects

Whole coating detached from substrate or individual layers one from another. Sometimes adhesion defects can only be noticed after an external influence such as stone impact.

    Cause/damage pattern:

  • Substrate not adequately prepared (rust, grease, moisture, sanding, cleaning).
  • Unsuitable material used.
  • Drying times, flash-off times too short.
  • Base paint not sprayed wet-in-wet, instead the intermediate drying times were too long.
  • Failure to intermediate sand.
  • Condensation formed because of temperature fluctuations.
  • Unprofessional preparation (especially on plastics).
  • Overheated CDP/intermediate filler.

    Repair of damage:

  • Sand out the damage and recreate the paint finish. Create the paint finish strictly in accordance with the general technical information.

Adhesion defects in clear lacquer.

Clear lacquer detched from base paint.

    Cause/damage pattern:

  • Base paint layer too thick.
  • Intermediate and final flash-off times of base paint too long.
  • Incorrect mixture ratio clear lacquer/hardner.

    Repair of damage:

  • Refinish sanding and recreate the paint finish.

Sanding scores

Single or wide area clusters of scoring or sanding marks, often with raised edges. Noticeable on metallic paints as light-dark stripes.

    Cause/damage pattern:

  • Stopper sanded too coarsely.
  • Filler sanded too coarsely.
  • Filler not thoroughly dried bfore sanding.
  • Old paint sanded too coarsely.
  • Soft elastic substrates, e.g. TPA base, treated with thinners which was too aggressive and therefore etched.
  • Top coat applied too thinly.

    Repair of damage:

  • If the damage pattern is minimal, after the top coat has dried fine sand the paint surface and refurbish by polishing.
  • If the damage is great or on metallic paints, sand the paint surface or substrates and if necessary remove them, then cover the bare metal and re-paint.

Formation of stripes

Differing, stripe shaped color/effect formations in dark/light areas of a metallic paint finish.

    Cause/damage pattern:

  • Spray gun (nozzle) not perfect.
  • Incorrect spray pressure.
  • Thinners not suitable.
  • Incorrect spray viscosity.
  • Flash-off time too short.
  • Unsuitable working temperature.

    Repair of damage:

  • Apply base paint evenly.
  • Repair spray gun.
  • After clear lacquer has thoroughly dried, sand surface and paint again.

Peeling/blistering on plastic parts

Paint adhesion insufficient between top coat and filler and/or primer layer. It often happens that the whole of the paint finish detaches from the plastic.

    Cause/damage pattern:

  • Plastic item not cleaned sufficiently, not or inadequately tempered.
  • Unsuitable cleaning agent used.
  • Unsuitable materials used.
  • Moisture.
  • Paint finish underbaked or overbaked.
  • Poor or lack of intermediate sanding.

    Repair of damage:

  • Sand away faulty paint coats and re-apply paint finish.
  • In extreme cases use a new part.

Blistering on polyester material

Color shade differences or marks in paintwork subsequently applied to previously unpainted plastic material.

    Cause/damage pattern:

  • Plastic material is not suitable for painting.
  • Incorrect bonding agent.
  • Paint used not solvent resistant.

    Repair of damage:

  • Repaint using suitable materials.
  • Install unpainted new part (after consulting customer).

Peroxide marks in metallic paints

After longer period of drying, abnormal marks where the color shade varies.

    Cause/damage pattern:

  • Too much hardener added to polyester stopper (over 3% can cause this damage pattern).
  • Polyester stopper not well enough mixed.

    Repair of damage:

  • Sand, fill with polyester or epoxide filler and re-paint.

Crack formation

Cracks of different lengths and depths running in all directions.

    Cause/damage pattern:

  • Layers too thick.
  • Painted several times.
  • Temperature fluctuations.
  • Mechanical effects e.g. distortions.
  • Substrate not thoroughly hardened.
  • Old paint not completely dried out.
  • No or insufficient hardener added.
  • 2-component materials used on nitro or TPA.

    Repair of damage:

  • Sand away layers until sound substrate is reached and create new paint finish (prime, fill, apply topcoat).

Shrinking back/zone edge marks

Lifting or dropping in of edge zones (edges which accentuate themselves in the top coat), flow problems and loss of shine in top coat.

    Cause/damage pattern:

  • Old paintwork not rubbed down to a seamless transition.
  • Stopper and filler on a viscoplastic base primer.
  • Filler sanded and overpainted when not thoroughly hard.
  • Previous materials overworked too early, substrate not sufficiently hardened.
  • Primer applied in layers which were too thick, and not dried for long enough.
  • Sanding paper too coarse.
  • Top coat thinned too much.

    Repair of damage:

  • After hardening off the top coat, fine sand the surface and polish up, apply filler if necessary and paint once more.

Blistering

Small, spot-like, air-filled or water-filled blister shaped high-spots in the paint construction. Their dimensions can range from pin-head to pin-point size in a closed paint film. Arrangement and accumulation very variable. In the advanced stages, circular flaking of the paint from the substrate. These are neither boils nor corrosion.

    Cause/damage pattern:

  • Moisture absorption by substrate.
  • Insufficient drying of the substrate after wet sanding (especially on polyester material).
  • Humidity too high before painting; condensation formation because of temperature fluctuations.
  • Pores/sink holes in substrate not sanded out.
  • Polyester material not covered.
  • Sweat from hands.
  • Salts and minerals in sanding water.
  • Spray air contaminated.

    Repair of damage:

  • Sand away damage, matt sand remainder of surface, clean with silicone remover, fill and re-paint.

Etching

The base paint is etched by the clear lacquer. This causes the aluminum pigments to change their alignments. The color of the etched base paint seems more grey than that of normal base paint. Result is that the surface structure of the clear lacquer becomes increasingly more matt.

    Cause/damage pattern:

  • Base painted too wet.
  • No intermediate flash-off time.
  • Layers too thick.

    Repair of damage:

  • Sand and re-paint.

Paint wrinkles/puckering

Lifting/puckering of the paint surface.

    Cause/damage pattern:

  • First paint not hardened through or can be etched.
  • Areas of clear lacquer which were sanded through to base paint have not been not isolated with filler, or with unsuitable filler.
  • Unsuitable substrate (e.g. spray can painting with TPA or nitro).
  • Use of unsuitable primer, paint and thinner materials.
  • Paint systems not matched to each other.
  • In wet-in-wet process, specified flash-off times not adhered to.
  • Synthetic resin top coat (alkyd resin) worked over too soon.

    Repair of damage:

  • After thorough drying, completely remove the top coat together with the attacked substrate at the affected areas and re-create a new paint finish.
  • Before applying top coat, rub down the complete surface.

Cloud formation

Differing, blotchy color/effect formations in dark/light areas of a metallic paint finish.

    Cause/damage pattern:

  • Spray gun, spray nozzle, spray pressure not perfect.
  • Varying spray viscosity, spraying method, flash-off times, spray booth temperature.
  • Thinners not suitable.

    Repair of damage:

  • Droplet method before clear lacquer application.
  • After clear lacquer has thoroughly dried, sand surface and re-paint.

Spots

Points rising up from the paint film.

    Cause/damage pattern:

  • Metallic base paint sprayed too dry, so that the metal particles could not incorporate into the paint. The clear lacquer could not cover these vertical standing particles because the spray air was too hot or the booth temperature was too high.

    Repair of damage:

  • After the paint surface has dried, lightly sand it with grade P800 sanding paper, clean with silicone remover and re-apply clear lacquer.

Metamerism/color deviations

Noticeable when identical color shades undergo a change of hue as the light source changes (daylight/artificial light). Different pigment composition between original and repair paint.

    Cause/damage pattern:

  • Use of paints with pigmentation which was not compatible with the standard, e.g. a green can be formulated from yellow and blue, or directly from green.
  • Use of an unsuitable mixed or ready made paint to re-tone.

    Repair of damage:

  • Repaint using the correct paint.

Washing out

On paint which has been newly applied but not yet dried, the interaction of surface tension and very different specific gravities of the different pigments can lead to swirl-like turbulence which results in separation of the pigments.

    Cause/damage pattern:

  • Layer too thick, paint not stirred enough.

    Repair of damage:

  • Sand and re-paint.

Loss of gloss

Milky, dreary tarnishing of the paint with more or less even loss of gloss.

    Cause/damage pattern:

  • Cold with low air humidity.
  • Heat with high air humidity.
  • Substrate can be etched.
  • Hardener fault or wrong hardener used.
  • Paint thinned too much.
  • Proportion of pigment too high because of poor stirring.
  • Not optimum drying.

    Repair of damage:

  • After drying, remove the matt effect by polishing. If unsuccessful, rub down complete area and paint again.

Covering ability/areas of thin paint

Different color shades in the surface. The minimum layer thickness is not achieved here. The effects range from local minor shade variations through mottled spray zones to completely missing top coat.

    Cause/damage pattern:

  • No correct, uniform substrate (effect paint).
  • On three-layer systems, wrong filler.
  • Insufficient top coat application.

    Repair of damage:

  • Sand surface and recreate the paint finish.

Flow problems/orange peel

Surface structure bumpy, grained. The surface is similar to the peel of an orange.

    Cause/damage pattern:

  • Paint viscosity too high.
  • Use of fast evaporating, highly volatile thinners.
  • Booth temperature too high.
  • Spray gun distance too great, too little material applied.
  • Nozzle too large.
  • Incorrect spray pressure.

    Repair of damage:

  • Small surfaces: fine sand and polish.
  • Sand out the surface and recreate the paint finish.

Dirt embedded in metallic base paint.

Inclusions of contamination in metallic base paint, of different sizes and shapes (grains or lint).

    Cause/damage pattern:

  • Dust was not properly removed from the surface to be painted.
  • Paint material not sieved.
  • Function of the painting facilities not optimum.
  • Filter contaminated.
  • Wearing unsuitable clothing.

    Repair of damage:

  • Sand and repaint.

Dirt embedded in top coat

Inclusions of contamination in top coat or under paint layers, of different sizes and shapes (grains or lint). Optical adverse effect.

    Cause/damage pattern:

  • Dust was not properly removed from the surface to be painted.
  • Paint material not sieved.
  • Function of the painting facilities not optimum.
  • Filter contaminated.
  • Wearing unsuitable clothing.

    Repair of damage:

  • Single inclusions: after thorough hardening, sand out using 1200 - 1500 grade paper and repolish using a suitable silicone-free sanding or painting paste.
  • Large area contamination: sand and repaint.

Water marks

Ring shaped marks appearing on the paint surface.

    Cause/damage pattern:

  • Evaporation of water droplets on freshly painted and not yet fully hardened paint finishes (mostly only found on horizontal surfaces).
  • Layer too thick.
  • Drying time too short.
  • Hardening faults or hardener no longer useable.
  • Use of unsuitable thinners.

    Repair of damage:

  • Rub down only slight marks with sanding paper grade P1000 - P1200 and then polish.
  • For heavy marking, sand the surface matt, clean with silicone remover and repaint.

Paint runs

Wave-like paint run tracks in top coat or in an intermediate layer on vertical surfaces. Mostly in the area of swage lines, seams or openings (there they are paint runs, otherwise curtains).

    Cause/damage pattern:

  • Uneven paint application.
  • The specified viscosity was not complied with.
  • Use of unsuitable thinner materials.
  • Air, material or room temperature too low.
  • Layers too thick.
  • Spray gun (nozzle) not perfect.

    Repair of damage:

  • After thorough drying, sand unevenness flat, if necessary leave to dry afterwards.
  • Small areas of damage can be equalised using the paint plane, then sand, polish or repaint.

Swirl marks

Three dimensional appearance in the paint surface in the form of smears or blotches. This effect is intensified in direct sunlight.

    Cause/damage pattern:

  • Polishing using polishing machine on paint which has not yet hardened throughout.
  • Polishing intervals too long or none at all.
  • Pressure too high while polishing.
  • Incorrect polishing material or polishing tool.

    Repair of damage:

  • Allow the paint to harden completely and then polish.
  • If the damage is irreversible, rub down and apply new clear lacquer.

Tools and Equipment for Paint Repairs > < Factory Paint Application