8 paint defects.ppt

Paint SchoolJPS-E / Paint technology / 1

Paint Defects


DelaminationDelamination(Adhesion failure)(Adhesion failure)

Appearance• Loss of adhesion:

– Intercoat delamination: Between coats : – Substrate delamination : Between primer and substrate

Caused by• Primer not compatible with subsequent coat• Contamination of substrate or between coats• Recoating interval too long• Blooming / sweating

Repair• Remove loose paint layer or down to substrate • Recoat


Primer

Blast-cleaned steel

Topcoat

Oxygen Humidity Contamination

Topcoat

DelaminationDelamination(Intercoat Delamination)(Intercoat Delamination)

Intercoat delamination

Blast-cleaned steel


ChalkingChalking• Almost like dust on top of the coat• The gloss will be reduced

Pigments and extenders exposed on the paint surface, due to

• Exposure to sun / UV light• Weathering of the paint• Insufficient mixing stirring of the paint• Use of wrong thinner

• Grind top layer of the paint • Recoat

Appearance

Caused by

Repair


Blasted steel

Chalking

Epoxy topcoatPrimer

Sun light

ChalkingChalking


Bloom and BlushBloom and Blush(Blushing)(Blushing)

Appearance• Surface looks milky

Caused by• Condensation on cold steel surfaces at high humidity• Air pollution, sulphur dioxide (SO2) and ammonia forming

ammonium sulphate on the paint film.• “Fast “ thinners

Repair• Grind top layer of the paint • Recoat


Sweating and CarbonizationSweating and Carbonization(Amine Blooming)(Amine Blooming)

Appearance• Tacky and sweating film, often with white stainsCaused by• High humidity, particularly on Epoxies during curing• Poor ventilation• The Amines react with CO2 and humidity and form Amine

carbamate.• Too low temperatureRepair• Wash with warm water or thinner, using ragsPreventive measure: Induction time before application start


Blushing

Primer

Blasted steel

Wet paint

High relative humidity, condensation, rain drops

BlushingBlushingBloom / BlushBloom / Blush

From above

Blasted steel


Pinpoint RustingPinpoint Rusting

Appearance• Points of rust

Caused by• Small pores (pinholes), openings or defects in the paint

film down to bare steel• Holidays due to overspray, dry spraying etc.• Too high substrat roughness

Repair• Grind down to bare steel • Recoat


PrimerBlasted steel

Dry topcoat

Pin hole

Rust penetration

Pinpoint RustingPinpoint Rusting


PinholesPinholesAppearance• Tiny holes through one or more coats, or even down to the substrate, as if

perforated by a needle

Caused by• Dry spraying• Entrapped solvents or air• Porosity of previous coat• Incorrect application technique or viscosity of the paint



PinholesPinholes

PrimerBlasted steel

Wet topcoatSolvents / air

Pinholes


FisheyesFisheyes

Appearance• Spots of paint on the surface with no wetting of the surface

around the spots. Appearance of a fisheye.

Caused by• Paint applied on oil, silicone or other contaminants• Painted on incompatible paint (Glossy paint giving poor wetting)



Evaporation of solventsSilicon

FisheyesFisheyes

Wet topcoat

Primer

Blasted steel

Fisheye


WrinklingWrinkling

Appearance• Small wrinkles through or partly through the paint film

Caused by• Skin drying of the paint film, which is usually applied too

thick



WrinklingWrinkling

Wet topcoat

Primer

Blasted steel

Wrinkles


LiftingLiftingAppearance• Small wrinkles through the paint film

Caused by• Softening and raising or wrinkling of a previous coat by

the application of an additional coat• Lifting often caused because the solvents in the new coat is

too strong for the previous coat

Repair• Remove the paint • Recoat


LiftingLifting

Wet topcoat

Primer

Blasted steel

Wrinkles

Lifting


Mud-crackingMud-cracking

Appearance• Cracks occurring during the drying process of the paint• Appearance of the surface of cracked mud

Caused by• Particularly for inorganic Zinc applied at a too high film

thickness

Repair• Re-blast to Sa 2½ or grind off• Apply the inorganic Zinc


Primer

Blasted steel

Mud-crackingMud-cracking


Dry SprayDry Spray

• Porous, sandpaper like surface of the paint• Poor atomisation of the paint• Spray gun too far away from the object• High air temperature and low relative humidity: Too

fast evaporation of the solvents• Strong wind during application• Inorganic Zinc: Re-blast and apply new paint• Physically drying paints: Apply thinner on the

painted surface and apply a new coat• Oxidativly drying paints: Remove loose dust and

apply topcoat• Two-pack paints: Remove loose dust, sandpaper to

smooth surface, apply topcoat

AppearanceCaused by

Repair


Dust from application

Primer

Blasted steel

Dry SprayDry Spray


BleedingBleeding• Discolouration of a paint, particularly in

topcoats• Coloured ingredients in a previous coat or

on the substrate is dissolved by solvents in the subsequent coat, e.g.

• Soluble pigments (Poor solvent resistance• Tar, Bitumen, etc.• Surface contaminants (coloured)• Re-blasting and re-application

Note:Note: Bleeding may continue through additional coats unless source is removed

Appearance

Caused by

Repair


BleedingBleedingWhite topcoatTar containing primerBlasted steel

DiscolourationBleeding


Orange PeelOrange Peel

• Paint surface is rough, like an orange peel

• Poor flow / levelling properties of the paint (Paint too thick or too low temperature)

• Poor atomisation of the paint• Too fast evaporation of the thinner• Airless spray gun too close to surface

• Improve application technique• Use correct thinner • Grind surface and apply new paint

Appearance

Caused by

Repair


Orange PeelOrange Peel

Seen from above

Wet topcoat

Primer

Blasted steel


Sags and RunsSags and Runs

Appearance• Paint running or hanging like curtains on vertical surfaces

Caused by• Too high Wet film thickness• Too much thinner added to the paint• Airless spray gun too close to surface

Repair• Avoid above • Use small paint brush to smoothen or remove excessive

paint


Sags and RunsSags and Runs


Cratering / PoppingCratering / PoppingSolvents or air try to evaporate through the upper part of the film, which has already nearly dried, leaving small bubbles /craters on the surface

• Very porous substrate (e.g. Zinc silicate primer)• Entrapped solvents or air in the paint film• Usually in connection with too high film thickness,

too long application distance or too strong ventilation.

• Reduce film thickness or ventilation and adjust application technique (Tie coat / mist coat technique.

• Remove paint on painted surfaces and repaint

Appearance

Caused by

Repair

8 paint defects.ppt

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