Inver Istituzionale

Industrial Coatings

Select your problem as below

  1. Product category#

  2. Problem typology

  3. Problem

ABSORPTION

This occurs when the undercoat absorbs the enamel above causing a loss of brilliance of the enamel.

Causes

  • Overpainting interval too short.
  • Quantities applied not suitable.

Remedies

  • Allow more time to pass between the undercoat and the enamel topcoat.
  • Sand the undercoat.
  • Apply the greatest possible quantity of enamel in a number of passes at intervals.

BLISTERING

Blistering can be seen as bubbles of varying size and density. Very often it is accompanied by a detachment of the paint film from the piece or between one coat and another. This phenomenon is visible after exposure outdoors or after laboratory simulation tests (salt spray and humidity).

Causes

  • Poorly cleaned piece or insufficient rinsing after pre-treatment.
  • Poor adherence between one coat and another.
  • Paint cycle unsuitable to resist environments with high humidity.
  • Excessive quantity of product applied.

Remedies

  • Improve the cleaning of the piece, check the pre-treatment equipment.
  • Do not wait too long between one coat and another, try sanding before painting over the previous coat.
  • Use a higher performance paint cycle.
  • Apply the thicknesses suggested by the supplier.

BURNING / BUBBLING

This can be seen as craters or spikes and may occur in air dried and oven dried products.

Causes

  • Coat of paint too thick.
  • Ambient temperature too high.
  • Poor pulverisation.
  • The Thinner used is too rapid
  • The drying time is too short.
  • The oven temperature is too high.
  • Heating curve of the oven is too steep (rapid).

Remedies

  • Reduce the thickness.
  • Reduce the temperature in the booth.
  • Improve the pulverisation of the product by diluting it more or adjust pressure.
  • Check the nozzles for wear.
  • Use a slower thinner.
  • Increase the drying time before placing in the oven.
  • Check the oven temperature and the heating curve.

ORANGE PEEL EFFECT

This is produced by poor spreading of the film applied.

Causes

  • Viscosity too high during application.
  • Poor pulverisation
  • The thinner used is too rapid
  • The piece to be painted is too far from the nozzle.
  • The application equipment is unsuitable.
  • The ambient temperature is too high.
  • The piece is hot.

Remedies

  • Dilute the product further.
  • Optimise the nozzles and working pressure.
  • Use a slower thinner.
  • Move the piece closer to the nozzle.
  • Use application systems suitable for producing smooth surfaces
    (for example mixed-air)
  • Apply at a lower ambient temperature and on a cooler piece.

EXCESSIVELY SLOW DRYING

When the drying time and handling time is longer than normal.

Causes

  • Excessive thickness of the coat applied.
  • Low ambient temperature.
  • The thinner used is too slow.
  • The product has aged too much in the can. Products which dry by oxidisation with the air (see rapid drying enamels) may have lost a part of the drying additives.
  • The wrong dose of one of the components (this applies to two component products).
  • Application on undercoat not suitable.

Remedies

  • Reduce the thickness (for example by further dilution or reducing the flow through the nozzle).
  • Establish suitable ambient conditions (Temperature = 20-25°C and max. humidity 50–70%).
  • Use a faster thinner.
  • Avoid long periods of storage
  • Prepare the two component mixtures carefully.
  • Make sure that the painting cycle is suitable.

OPAQUENESS

This occurs when the paint film becomes opaque during drying without having been exposed to severe conditions.

Causes

  • Unsuitable ambient temperature and humidity.
  • The thinner used is too rapid.
  • the piece has not been prepared adequately (presence of grease and/or humidity).
  • Poor pulverisation.
  • Presence of contaminants in the application equipment.

Remedies

  • Establish optimal ambient conditions (temperature = 20-25°C and humidity 50-70%).
  • Use a slower thinner.
  • Clean the piece thoroughly making sure that it is completely dry.
  • Optimise the viscosity, pressure and nozzles.
  • Check the condition of the application equipment.

WRINKLING

This occurs particularly with synthetic products that dry in air.

Causes

  • Excessive thickness of the coat applied
  • Ambient temperature too high during drying.
  • Painting over a quick drying enamel too soon or too late.
  • The product used for overpainting is to aggressive.

Remedies

  • Apply thinner coats of the product (dilute further or reduce the nozzle flow rate).
  • Lower the temperature during application and drying.
  • Keep to the times for overpainting indicated by the supplier.
  • Use a less aggressive thinner to dilute the finishing product.

PEELING

A coat of paint detaches from the piece or an undercoat.

Causes

  • Insufficient cleaning of the piece.
  • Hardening of the coat not yet completed.
  • Product not suitable for guaranteeing adherence to the piece.
  • Excessive ageing of the undercoat (especially if outdoors).
  • Application of the topcoat insufficient and extremely dry.
  • Undercoat with surface additives.
  • Paint cycle not suitable.

Remedies

  • Better cleaning of the piece.
  • Wait for the film applied to harden completely before checking adherence.
  • Use products specially produced to adhere to the piece.
  • Sand the coat underneath before overpainting.
  • Increase the quantity of product and apply more abundantly.
  • Make sure that the coat underneath does not contain surface additives that may inhibit adherence (silicon based).
  • Contact the supplier for a suitable paint cycle.

POOR COATING

This may occur obviously during application with electrostatic systems and is noticeable when there is poor covering, with a wastage of paint or a blow back of powder towards the operator or application machine.

Causes

  • Inefficiency of the application machinery.
  • Shape of item to be painted unsuitable.
  • Incorrect distance from the part to be painted.
  • Applicator isolated from the ground.
  • Part to be painted not electrically earthed.
  • Poor coverage of powder
    (the particles drop before reaching the part to be painted).
  • Unsuitable paint product and/or thinner.

Remedies

  • Check that the application system and other components are working properly.
  • Check the electrical earth of the piece (check that the hooks are clean).
  • Improve the powder coverage (increase dilution, check the nozzles and pressure).
  • Change the type of thinner in order to remain within the correct range of resistivity values.
  • Eliminate particularly difficult corners (Faraday cage effect).
  • Move the piece to be painted closer or further away.
  • Check that the applicator is not insulated from earth by checking that the area where it works is clean and make sure that the shoes worn are suitable.

RUNNING AND DRIPPING

This may occur during or immediately after in the drying phase.

Causes

  • Poor powder coverage.
  • The coat being applied is too thick.
  • Piece too close to the nozzle.
  • Ambient temperature or piece temperature too low.

Remedies

  • Optimise the viscosity of the product (it is usually necessary to increase the dilution).
  • Check the pressure and condition of the nozzles.
  • Reduce the thickness or apply more coats at intervals.
  • Move the piece away from the nozzles.
  • Heat the ambient environment and the piece.
  • Use a faster thinner.

POOR COVERING

The colour of the piece shows through even though the thickness applied is sufficient.

Causes

  • The paint colour is unsuitable for covering the colour of the piece (see very intense yellows and reds).
  • Product not mixed correctly.
  • Poor coverage of powder (droplets too large).
  • Excessive dilution.

Remedies

  • Use an undercoat of enamel in the desired colour.
  • Mix the product well.
  • Improve the pulverisation adjusting the viscosity and pressure and checking the condition of the nozzles.
  • Increase the viscosity.

CISSING

This appears in the form of small "craters" which open and uncover the surface underneath or undercoat. Usually they become visible during application or immediately after.

Causes

  • Greasy surface.
  • Contamination of the application system with oil or water.
  • Contamination of the paint product or thinner with silicon based additives.
  • Contamination of the painting area.
  • Incompatibility of the product fumes used in the same area.

Remedies

  • Clean the piece more thoroughly.
  • Eliminate the causes of contamination of the application equipment (oil or water leaks).
  • Eliminate the causes of contamination of the product checking the equipment that comes into contact with it (spatulas, gloves, containers, etc.)
  • Make sure that silicon based products are not used in the area (hammered effects, waxes, polish, etc.)
  • Avoid the simultaneous application of incompatible products.

POWDER LOSS

this occurs when powder is deposited on another powder layer without being absorbed by it. The consequence is a loss of aesthetic quality of the film.

Causes

  • Thinner too rapid.
  • Unsuitable application system.
  • Wrong painting system.
  • Ambient temperature too high.

Remedies

  • Use a slower thinner or add a suitable inhibitor.
  • Reduce the quantity of air in the application equipment.
  • Paint the part in a different way so that the points where the powder presumably drops are well covered.
  • Reduce the temperature in the booth.

WASTAGE

This occurs when the quantity of product used is greater than the standard amount.

Causes

  • Application system not suitable for the piece.
  • Poor pulverisation of the powder.
  • Poor coverage by the paint product.
  • Piece too far from the nozzle.

Remedies

  • Choose a more suitable application system (airless, electrostatic, etc.)
  • Optimise the nozzles and pressure.
  • Check the product viscosity.
  • Move the piece closer to the nozzle.

SKIN

Skin forms on products when the surface dries in contact with the air.
It is almost always possible to use the product after removing the layer of skin and filtering the rest of the product just to be sure that no skin remains.
If the paint is not to be used, remove the skin and pour a layer of thinner gently over the surface without stirring.

Causes

  • The can has not been closed tight
  • The can is not full enough (leaving excessive space for air)

Remedies

  • Check that the can is tightly closed
  • Top up the can

SEDIMENTATION

The differing specific weights of the paint components makes sedimentation almost inevitable; it is important that the bottom layer can be mixed back into the rest of the product.

Causes

  • Product stored too long.

Remedies

  • Avoid storing for long periods.

WRONG COLOUR

It is important to make sure that there really is an error, avoiding judgements made on the product without mixing and applying the paint properly.

Causes

  • Presence of bottom layer deposit not mixed in.
  • Incomplete coverage of the surface painted (bottom colour coming through).

Remedies

  • Mix the product properly until fully mixed.
  • Apply a greater thickness to cover the underlying surface with additional thin coats.

EXCESSIVELY HIGH VISCOSITY

In these cases it is important to make sure that the paint is not thickened to the point of being unusable (livering); the usual cause is storage at excessively high temperatures.

Causes

  • The can has not been closed tight.
  • Very low ambient temperature (viscosity is measured at a temperature between 20 and 25°C).

Remedies

  • Check that the can is closed tightly.
  • Adjust the temperature of the product to the correct value.

OPAQUE OR DIFFERENT COLOURED FILM

Film more opaque than expected or discoloured.

Causes

  • Oven temperature too high.
  • Oven time too long.
  • Contamination with other types of powder (incompatibility).
  • Contact during heating with vapours (water, solvents) o with combustion gases from the burner which may come directly from the oven.

FORMATION OF CRATERS

Causes

  • Contamination with other types of powder.
  • Insufficient grease removal or defective pre-treatment.
  • Contamination with other incompatible substances (for example, silicone).
  • Oven temperature increase too rapid.

INSUFFICIENT FILM THICKNESS

Causes

  • Insufficient powder delivery.
  • Nozzle blockages.
  • Electrostatic field too weak, spray nozzles too far from the supports or very dirty hooks.
  • Chain speed too high.
  • Powder particle size too fine, the individual particles do not become charged sufficiently and their weight exceeds the force of the field

PRESENCE OF SMALL BODIES

Presence of small bodies, lumps or other coarse particles.

Causes

  • Defective pre-treatment (check the washing).
  • Dirty metal surface.
  • Insufficient sieving of the powder.
  • Powder compacted due to excessive temperature during storage.
  • Damp powder.

POOR COVERING PROPERTIES

Poor covering with the formation of pitting

Causes

  • Temperature increase of the pieces too slow or too fast in the oven.
  • Storage too long or in unsuitable conditions.
  • Contamination caused by excessive humidity.
  • Powder unsuitable for rapid bonding.
  • Electrostatic voltage too high.
  • high application pressure.

EXCESSIVE FILM THICKNESS

Causes

  • Powder delivery too high.
  • Electrostatic field too strong.
  • Too many nozzles for the requirement.
  • Time in the spray area too long.
  • Manual retouching excessive or incorrect.

BLOCKED PISTOLS

Causes

  • Melting of the powder in the pistols or nozzles.
  • Contamination of the powder with coarse foreign materials.

POOR FLUIDISATION OF THE POWDER

Poor fluidisation of the powder in the container.

Causes

  • Air pressure in the container too low.
  • Fluidisation membrane blocked.
  • Humidity too high in the compressed air.
  • Humidity too high in the powder.
  • Poor fluidisation properties of the powder.

BLOCKED HOSES OR VENTURI TUBES

Causes

  • Melting of the powder in the hoses and Venturi tubes.
  • Poor transport properties of the powder.
  • Powder formulation unsuitable for the characteristics of the equipment.

IRREGULAR POWDER FEED

Irregular powder feed with asymmetrical delivery.

Causes

  • Worn parts of the pistol
  • Blockage by melted powder
  • Pipes, Venturi or nozzle blocked with hard compacted powder
  • Irregular air delivery due to excessively low pressure
  • Incorrect grinding (particle size) of the powders

DISCONTINUOUS POWDER FEED

Causes

  • Insufficient air pressure
  • Pipes squashed or completely crushed
  • Venturi pumps blocked

FORMATION OF SPARKS

Causes

  • Voltage of the current too high.
  • Electrical charges form in the pipes for triboelectric charging of the powder during transport.
  • Unsuitable pipe material.
  • Incorrect earthing.

INSUFFICIENT ADHERENCE OF THE POWDER TO THE PIECES

Causes

  • Incorrect earthing of the conveyor chain, insulated hooks.
  • air pressure too high.
  • Nozzles too far from the pieces.
  • Air suction in the cabin too strong with consequent formation of turbulence.
  • Generator voltage too low.
  • Powder too coarse.

INSUFFICIENT COATING

Insufficient covering of the pieces by the powder.

Causes

  • The generator does not provide a high enough voltage to the electrodes.
  • Insufficient earthing.
  • Excessive powder feed.
  • High humidity in the air in the spray booth.
  • Damp powder.
  • Excessive air pressure.
  • Chain speed too high.

IRREGULAR MOVEMENT OF THE POWDER CLOUD

Causes

  • Air in the cabin too dry.
  • Insufficient powder delivery.
  • Inefficient suction of air from the cabin.

REPULSION OF THE POWDER BY THE PIECES

Causes

  • Voltage of the current too high
  • Pistols positioned too close to the pieces to be coated.
  • Insufficient earthing

POOR PENETRATION OF CAVITIES

Poor penetration of cavities and corners (Faraday cage effect)

Causes

  • Insufficient delivery of powder.
  • Insufficient earthing.
  • Voltage too high.
  • Air pressure too high.
  • Wrong position of the pistols.
  • Powder particle size too fine.

CONTAMINATION OF THE POWDER RECOVERED

Causes

  • Recovered powder sieve broken, missing or inefficient.
  • Flakes of hardened powder or dropping of material from the transport hooks in the cabin.
  • Impurities or dirt present in the air in the spray cabin.
  • Impurities or particles still present on the pieces to be coated.

EXCESS POWDER

Excess powder in the recovery container

Causes

  • Compacted powder blocking the recovery system.
  • Broken hose type filters.
  • Powder ground too fine.
  • Unsuitable cyclone suction.

SPRAY CABIN COVERED IN POWDER

Spray cabin covered in powder and insufficient air circulation.

Causes

  • Blocked bag or cartridge filters.
  • Blocked powder recovery sieve.
  • Powder feed too high.
  • Opening of the spray cabin too wide.

POWDER LEAKING FROM THE CONTAINER

Causes

  • Air pressure too high.
  • Particle size of the powder too small.

CAVITIES IN THE SURFACE LAYER

Presence of cavities in the surface layer of the powder in the container.

Causes

  • Powder level too low
  • Damp or compressed membrane
  • Economical quality of powder

POOR FLUIDISATION OF THE POWDER IN THE CONTAINER

Causes

  • Powder particle size too fine.
  • Fluid bed with blocked filter.
  • Fluid bed filter mesh too fine.
  • Economical quality of powder.
  • Presence of dampness.

SEPARATION OF THE POWDER INTO TWO LAYERS

Separation of the powder into two layers (fine and coarse powder)

Causes

  • Powder level too low.
  • Powder particle size too fine.

APPEARANCE OF STAINS ON THE SURFACE

Appearance of more opaque or discoloured stains on the surface.

Causes

  • Mistakes in the pre-treatment.
  • Presence of oil or grease on the surface of the pieces.
  • Presence of other metals or alloys (for example, copper, brass which may be the cause of the discolouration).
  • In the case the galvanised surfaces the presence of oxidation products may cause stains.

CONTAMINATION OF THE POWDER

Causes

  • Type of powder recovery system.
  • Fresh powder contaminated.

INSUFFICIENT HARDNESS AND RESISTANCE TO ABRASION

Causes

  • Insufficient heating.
  • Unsuitable powder.

YELLOWING OF THE FILM

Causes

  • Combustion gas present in the oven.
  • Oven time too long.
  • Oven temperature too high.

POOR FLEXIBILITY AND RESISTANCE TO IMPACT

Causes

  • Insufficient heating.
  • Insufficient grease removal or pre-treatment.
  • high film thickness.

FILM SHRINKAGE

Film shrinkage on corners with poor coverage of the surface.

Causes

  • Oil residues.
  • Incomplete drying of the pieces.
  • Insufficient grease removal.

POOR BRILLIANCE

Causes

  • Insufficient film thickness.
  • Powder not completely compatible.
  • High temperature during heating.
  • Heating curve of the oven too slow with problems in the melting phase.

POOR FLEXIBILITY AND RESISTANCE TO IMPACT

Causes

  • Insufficient heating.
  • Insufficient grease removal or pre-treatment.
  • high film thickness.

POOR RESISTANCE TO CORROSION

Causes

  • Poor grease removal or unsuitable pre-treatment.
  • Insufficient heating.

POOR RESISTANCE TO CHEMICALS

Causes

  • Insufficient heating.
  • Unsuitable quality of the powder.

INSUFFICIENT COATING

Causes

  • Electrostatic charge of the powder too low (contact the equipment manufacturer).
  • Insufficient earthing (clean the hooks)
  • Insufficient delivery of powder from the nozzles.
  • Unsuitable pulverisation of the powder (contact the supplier).

INSUFFICIENT PENETRATION OF CAVITIES BY THE POWDER

Penetration of the cavities by the powder and corners insufficient.

Causes

  • Poor powder delivery.
  • Insufficient earthing.
  • Powder cloud issuing from the nozzles too large.

POWDER NOT ADHERING TO THE PIECES

Powder not adhering to the pieces or powder falling off them easily.

Causes

  • Electrostatic charge of the powder too low.
  • Powder delivery too high or compressed air pressure too high.
  • Unsuitable particle size distribution of the powder.

INSUFFICIENT POWDER FEED

Causes

  • Blockage due to melted powder.
  • Presence of humidity in the air.
  • Excessively high air pressure.
  • Worn Venturi tubes.
  • Excess of powder in the pipes.
  • Powder particle size too coarse or too fine.
  • Particulate composition of the powder (some resins have a greater tendency to melt due to impact).

BLOCKING DUE TO MELTING OR FORMATION OF HARD LUMPS

Causes

  • The powder does not fluidise
  • Worn Venturi pumps
  • Compressed air pressure too low.
  • Blockage caused by dirty powder
  • Pipes squashed or completely crushed
  • Powder packed hard
  • Particle size too coarse