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1(Client Name)Paint Film Defects and Solutions
by Anthony T. Manuel TSD Senior Coating Advisor Hempel Paints
(Saudi Arabia)(Training Location)(Training Date)
2PAINT FILM DEFECTS AND SOLUTIONSBLEEDING
BLEEDINGBLEEDING - Shows as a surface discoloration. Caused by
an underlying colour or stain which gradually migrates through a
newly painted surface. This can be caused by Bitumen, Creosote,
Water-staining, Nicotine, and Pigmentation in previous coatings,
especially when recoating Water-based paints with strong
Solvent-based paint/lacquer.SOLUTION: All affected paint should be
stripped-off, and/or in the case of bleeding, sealed-off with an
appropriate sealer. After effective sealing, re-paint according to
the appropriate specification.
WRINKLING
WRINKLING
WRINKLING
WRINKLINGWRINKLING - Wrinkling of a paint is often caused by
applying the paint too thickly. The surface of the paint dries to
form a skin and the under surface remains soft and in a semi-dry
state for a considerable time. This results in movement within the
paint film and resulting stresses cause the top skin to wrinkle.
Can also occur during very rapid drying in hot weather.SOLUTION:
Remove the defective coating, abrade, clean , and recoat.FLAKING /
PEELING
FLAKINGFLAKING - This results from the splitting and lifting of
a paint coat or paint system due to loss of adhesion. This can be
due to one or more causes, such as:1. Paint being applied on top of
a chalking substrate or other powdery surface.2. Using a primer
which is not suited to the surface, such as underbound,
over-thinned primer or one liable to degrade on cement/alkaline
surfaces.3. Painting on old, poor quality paint, which can become
brittle & fail rapidly once disruptions occurs.4. Moisture
penetrating into wood causing movement which cannot be tolerated by
the paint system.SOLUTION: Flaking paint & adjacent areas of
suspected weakly adhering paint should be removed completely. When
repainting, care should be taken to provide a dry surface free from
powdery particles and that the surface is well sealed. Ensure
correct sealers/primers are used.
CRACKING
CRACKING
CRACKING
CRACKINGCRACKING - Rupture or breaking of the paint film
typically non-directional and caused by the application of
excessively high film thickness or the over-coating of a soft paint
with a hard one (ex. Physical-drying over-coated with
chemically-curing paint). Can also be caused by the stresses in the
substrate transferred to the paint.SOLUTION: Abrade to remove the
cracked paint and re-apply the coating system or use a more
flexible system that is not prone to cracking.
CHALKING
CHALKINGCHALKING - This is a powdery residue formed on a paint
finish when the surface begins to erode from exposure to the
weather. Chalking is not usually considered a defect unless it
occurs prematurely. A good gloss paint may soon begin to chalk if
used over a porous surface, e.g. caused by the non-use of a primer
or sealer over-thinning of previous coats resulting in insufficient
sealing of the substrate. Chalking of surfaces can also be evident
where a saponifiable coating has been used and has degraded, i.e.,
by chemical attack.SOLUTION: Light chalking can be removed by
washing with water and detergent, and then repainted normally.
Heavy surface chalking must be brushed-off and a sealer applied to
bind the surface before painting.BLISTERS
BLISTERS
BLISTERINGBLISTERING - Takes place due to poor adhesion between
the paint and the surface. It may be caused by surface dampness or
excessive atmospheric moisture when painting. Blisters are often
caused by vapour pressure which builds up under a relatively
impervious paint film when moisture in the surface is subject to
heat, such as exposure to the sun. Dampness in the surface may be
due to moisture retained in the plaster or wood, or moisture
migrating from an adjacent structure.SOLUTION: All defective paint
(blistered film) must be removed. Surfaces must be cleaned, made
sound, then treated as new and painted according to
specification.
CRATERING / BLISTERING
SAPONIFICATION
SAPONIFICATIONSAPONIFICATION - Formation of a soft, cheesy
(greasy-feel) film under the coating due to the reaction between
the oil (in alkyd) and the alkaline substance in the substrate
forming a soap.
SOLUTION: Remove the saponified paint, abrade, clean and
re-apply a more suitable coating system that is
non-saponifiable.
SAGGING24SAGGING
TEAR
SAGGING WITH TEARS
SAGGING / RUNS
RUNS / SAGS
SAGGINGSAGGING - The downtrend movement of a coat of paint,
usually caused by uneven application or the wet edge being left too
long, or sometimes the use of too slow a thinner. On a plain
surface this may not produce individual runs but a thick lower
edge, which is sometimes referred to as curtaining.
SOLUTION: Rectifying this defect is not possible until the
thicker paint runs and sags have dried. The surface should be
flattened using wet and dry abrasive paper. To avoid the effect
ensure even application, cross-brushing and lay-off evenly.
ORANGE PEEL
ORANGE PEELORANGE PEEL - Similar appearance of the paint film to
a citrus fruit skin. Caused by paint viscosity problems or
applicator technique. Cosmetic in nature and does not have any
effect on the paint performance.
SOLUTION: The surface should be made even by sandpapering and
then applied with another coat after dusting-off to make an even
finish.
PINHOLES / HOLIDAYS
PINHOLES / HOLIDAYSPINHOLES / HOLIDAYS - Tiny holes, deep down
in the paint film caused by the bursting of entrapped solvent or
air within the paint film. Can also be caused by incorrect spray
application and solvent blend.
SOLUTION: Abrade affected area, clean and apply suitable
tie-coat/undercoat and topcoat as necessary.ORANGE PEEL WITH
PINHOLES
BLOOM
BLOOM
BLOOMINGBLOOMING - Hazy deposit on the paint film caused by the
migration of the free-amine in the curing agent of the epoxy with
the condensing water on the surface (due to low substrate
temperature).
SOLUTION: Abrade to remove the paint and re-apply the coating
system. CONCRETE
BLISTERS40
EFFLORESCENSE41EFFLORESCENCE - It is recognisable as a white
crystalline deposit of water soluble salts which may form on new
plaster, cement render and brick caused by drying out of the
structure. Efflorescence may also form blisters in a paint film
with no visible salts. Also, efflorescence salt may be attached to
the back of the paint film, causing no visible disruption, but
weakening adhesion and remaining a threat to future
decoration.SOLUTION: Remove by bushing down, DO NOT WASH-OFF.
Repair any damage which may be causing water ingress. Surfaces
should not be sealed or painted in alkyd or solvent based systems
until efflorescence ceases. Whilst efflorescence is present, porous
emulsion paints are recommended.EFFLORESCENCE
MOULD GROWTH43MOULD GROWTH - Usually occurs in damp or humid
conditions and can be seen as Fungal (Black Growth) or Algae (Green
Growth) both internally and externally.SOLUTION: Correct
ventilation and removal of condensation will solve many mould
related problems internally. In extreme cases treatment of growth
with household bleach is advisable before application of a
fungicidal treatment. For persistent problem areas, repaint with
paint products with anti-fungicidal properties.MOULD GROWTH
THANK YOU FOR YOUR ATTENTION
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