coating failures 2005-06
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34 June 2005 CleanerTimes
hy are we talking about paint
failures in this magazine? Many companies
doing pressure washing and waterjetting
also do paint application. They deal with
decks, garages, exteriors of houses, metal
buildings, and for the most part, leave the
large commercial jobs to painting contrac-
tors. Pressurized water is an excellent tool
to clean surfaces and remove old paint and
rust and debris prior to repainting.Historically, the most common cause of
paint failure is the preparation of the surface.
What is a paint failure? When a guarantee is
given, a paint failure must be defined care-
fully. For example, are sags, blisters, peeling,
color change, or cracking to be expected? If
so, how much, if any, can be tolerated?
Let me borrow from Driskos terms:
Afailure of coating is the loss of a coat-
ings function or purpose, i.e. when it no
longer protects the substrate, provides
an attractive appearance, or serves some
other function such as a non-slip. The time
of failure is considered to occur when some
action is needed to restore its properties to
the level necessary to again provide its
intended purpose.
Catastrophic coating failure is very sud-
den, very dramatic, and serious.
A defect is a film or surface flaw, deficien-
cy, or incompleteness that deviates from a
specification or industry-accepted condition.
VIEWPOINT
Coating Failuresby Lydia Frenzel, Ph.D.
W
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CleanerTimes June 2005 35
Degradation is a gradual loss of
coating and/or properties result-
ing from service condition and
weathering.
A premature failure occurs sig-
nificantly before the end of a coat-
ings life expectancy.
The service life of a coating is the
period of time during which a coat-ing provides its intended function.
This time will vary with different
exposures and services.
We typically think of premature
catastrophic coating failures as the
criterion for a warranty. However,
sometimes just the loss of gloss in
an area that is cosmetic is a serious
coating failure, even though it does-
nt affect the protective property
or lifetime. In any event, if the coat-
ing is expected to last 10 years in thatparticular service, you dont want
to have to repaint after six months.
Coatings are made different-
ly for interior or exterior use. Coat-
ings are formulated differently for
wood, concrete, plastic, drywall,
and steel or other metals. Coatings
are made differently for dry, hot
services as compared to damp,
cool surfaces (such as a bathroom).
Proper selection of coating is ex-
tremely important.We can break coating failures
down into problems associated with
the coating itself, problems between
the old coating (or substrate) and the
new coating, problems arising from
improper coating application, and
problems from poor surface prepa-
ration. More and more, power wash-
ing and waterjet cleaning are used
in surface preparation. Incompati-
bilities between coatings or coat-
ings and substrates and improper
coating application cannot be re-
medied by surface preparation.
I am working on my old house
and an old, old rental house. Here
are the problems that I am seeing:
chalking, discoloration, fading, loss
of gloss, adhesion failure, cracking,
organic growth (mildew, mold, and
algae), blistering, delamination,
peeling, flaking, and heavy, sagging
coats. There is nothing extraordi-
nary about this list.
As we work on cleaning surfaces,
stripping paint and putting on new
paint, I know that we have to take spe-
cial precautions around crevices,
areas where water can trap on the sur-
face, sharp edges, edges where bolts
or rivets have been placed (faying sur-faces), and limited access areas. There
are corners that we cant get into
and areas under sinks and tubs that
have been wet for years. Paints will
cut at the sharp edges, so we have to
grind or sand edges. Paints that
cover crevices, water pockets, bolts,
and limited access areas (I am lucky
to get any paint on some of the
places) will fail rapidly by cracking,
blistering, lifting, peeling, or flak-
ing and will allow bad things to hap-
pen under the paint.
The exterior coatings are sub-jected to the suns radiation, tem-
perature changes, and erosion. Some
failures come from causes inherent
to the specific formulation within the
coating itself.
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36 June 2005 CleanerTimes
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Chalking is the formation of loose powder on the
surface to give a dull finish. This normally happens
outside. How fast paint will chalk depends on the
formulation. Often, you can restore the gloss with a
pressure wash. However, if the formulation is not cor-
rect, the chalking will come back. A chalked surface that
has been cleaned with power washing is often considered
satisfactory for a new paint.
Erosion is the gradual loss of paint by wear and
weathering. This can happen inside, for example, when
you scrub on flat latex all the way through to the wall,
or outside. Erosion is a natural process; it is a failure if
it occurs very fast.
Discoloration is a change in the initial color after
application. Usually this is caused by exposure to
chemicals or to heat.
Fading is the reduction of color intensity, usually
by sunlight.
Loss of gloss is often associated with chalking,discoloration, and fading. Loss of gloss is cosmetic.
Mildew defacement (or algae growth) is caused
by growth of organisms. It is not only unsightly, but
could be a health problem. Growth of organisms can
be controlled by using EPA-approved biocides. Cleaner
Times has published articles on cleaning organic
growth. Organic growth normally doesnt affect
coating properties.
Brush marks can occur in coatings that have insuffi-
cient leveling for the wet film to flow together. Areas
with less film thickness will always deteriorate before
areas with greater film thickness.Adhesion failures are very common and can be
catastrophic. Typical failures are blistering, peeling,
and flaking.
Blistering can be caused by painting over salts, using
coatings with water-soluble components, and covering
a coating that is still trying to dry, thereby trapping
little pockets of solvent in the undercoat.
Figure 1
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Figure 1 is an example of heavy wrinkling of paint
that occurred within a month of painting in a bathroom.
Wrinkling can occur if too much thickness is applied
in one coat so that the paint doesnt cure properly. Thispaint is adhering everywhere else, but it appears in
this case that this particular area was not complete-
ly moisture free. The moisture on the substrate distorts
the wet film. The coating will have to be stripped and
recoated. This failure could happen if you were wash-
ing the woodwork or using a pressure washer and
didnt get the surface completely dried.
Blisters can occur where paint has been applied
over salts. Water penetrates the coating and collects at
the salt site. Figure 2 is an example of blisters that have
popped because of moisture penetrating the coating
at salt sites. Pressurized water is one of the surest
ways of getting rid of salts.
Incompatibilities include intercoat adhesion, de-
lamination, or peeling; the top coating attacking thebottom coating; and one coating shrinking/expanding
more than another coating. Limited adhesion and
subsequent peeling can occur when a water-borne
Figure 3
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CleanerTimes June 2005 37
Figure 2
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(latex) coating is applied over smooth oil-based enamel.
This is a very common problem in houses and in commercial
painting of smooth epoxy. The water-borne paint cannot
sufficiently attack the underlying coat to form a bond.
The topcoat shown in Figure 3breaks whenever it is hit,
and can be peeled back from the next coat. This latex
will have to be scraped or washed off, a bonding primer
used, OR the underlying paint has to be roughened,
before a new coating can be applied.Peeling or lifting can also occur when paint is applied
over oil or grease. A paint can crawl away from areas where
there is oil to form fish eyes, little areas of very low film
thickness. In kitchen areas, pressure washing with bicar-
bonate or a good detergent is often the solution to getting
the grease spatter off walls or floors.
As paints get old, cracking or
splitting can occur due to stresses.
When cracking occurs, generally a
path is opened to the substrate.
Cracking occurs in many forms:
checking, alligatoring, intercoat
cracking, and mud cracking. Crack-
ing can lead to flaking, rusting at the
crack, and loss of coating.
The paint failure shown in Figure
4 is common in old houses. It is the
peeling of thick, inflexible paint
from the substrate. Cracking and
flaking paint can also be found on
older steel structures.
Figure 5 shows an example of
failed paint that was applied dir-
ectly over mill scale. If the failure is
limited, the cure is to remove the
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Figure 4
Figure 5
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loose material, clean the surface,
and repaint.
These examples are coatings fail-
ures, but not premature coating fail-
ures. The coatings are approximate-
ly 1020 years old and were not
applied over the best of surface con-
ditions. They had a full life and are
just worn out. The repair for the fail-ures in Figure 4 and Figure 5 is
scraping, mechanical cleaning, or
power washing with glass beads or
soft abrasive to remove the coatings.
Sagging is a common problem.
Sagging is excessive coating applied
so that the weight causes the wet
coating to flow downward to form
sags, runs, or curtains as shown in
Figure 6.
We have just touched the sur-
face on some coatings failures andtheir causes. In 1982, Dr. Drisko
photographed 38 different failures.
You should get a copy of his Naval
Facilities Engineering Services Lab
monograph. And yes, I make liber-
al use of hot water, soap, scrub
brushes, and power washing to get
to the root of the problem.
References:
Richard Drisko, Chapter 12, Coating
Failures in SSPC Good Painting
Practices, Fourth Edition, Volume1, has a very good description of terms
and the types of paint failures for the
general practitioner.
TechData Sheet, Jun 1982, 82-08
Paint Failures-Causes & Remedies
was prepared by Dr. Drisco when he
was at the Naval Civil Engineering Lab
at Port Hueneme. It describes 38 coat-
ings failures with small colored pic-
tures. A single copy can be obtained by
writing Naval Facilities Engineering
Services Lab (NFESC), 1100 23rd Ave,
Port Hueneme CA 93043-4370. Multiple
copies (>10) generally cost a dollar each.
Lydia Frenzel, Ph.D. is executive
director of the Advisory Council. She is
an industry resource and works as a
proactive advocate for emerging tech-
nology. She shares her knowledge and
experience through custom courses, edu-
cational modules, and presentations.
Photos courtesy of Lydia Frenzel. CT
CleanerTimes June 2005 39
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