answers to some common questions about waterborne acrylic coatings
can be found below. If you cannot find the information that you
are looking for, please visit our Q&A
section, where you can submit a question.
Q: Can waterborne
acrylic coatings be used on steel?
A: Absolutely. A common perception is that if a waterborne coating
is applied to clean steel, the result will be rust. Although
steel will rust in the presence of water, oxygen and electrolyte
(salt), waterborne acrylic industrial coatings designed for
coating metal are formulated to inhibit the rusting of the steel
surface while the paint is drying. On the other hand, waterborne
paints not designed for coating steel, such as exterior house
paints, can lead to rusting known as flash rust. However, industrial
waterborne acrylics have been used successfully on steel and
other metal surfaces for 40 years in both field and factory
Q: What is flash rusting
and how can it be prevented?
A: Flash rusting is signaled by the presence of small rust spots
on the paint film, or sometimes by a tarnishing of larger areas,
and usually appears shortly after application and before the
coating is dry to touch. It generally results from slow drying
conditions, especially at high humidity, and is caused by the
migration of corrosion products through the paint film. It generally
does not affect long term performance, but detracts from the
coating’s appearance. Flash rusting can be eliminated
through proper formulation of the waterborne acrylic coating.
Inorganic salts such as sodium nitrite are typically added as
flash rust inhibitors. Avoiding application under extremely
high humidities is also recommended.
Q: Can I thin my waterborne
industrial paint with water to make it flow or spray better?
A: Waterborne paints are designed to be applied at the supplied
viscosity, and thinning should not be necessary. If thinning
is required, use only clean water and use it sparingly. Excessive
thinning will result in sagging, reduced film build, and possibly
performance problems. Always follow the manufacturer’s
Q: Are waterborne
acrylic coatings useful for immersion service?
A: While waterborne acrylic coatings can be successfully used
in many aggressive industrial environments, they are not recommended
for immersion service. Some waterborne acrylics, such as those
used for roof coatings, can withstand periods of contact with
pooled water, but they are not suitable for permanent immersion.
Q: Why aren’t
all waterborne coatings considered zero VOC (volatile organic
A: Although they are more environmentally-friendly alternatives
compared to many solventborne coatings, most waterborne acrylic
coatings do contain some volatile organic compounds, and thus
are not zero VOC. The organic compounds often enter the paint
formulation from co-solvents called coalescents, which are necessary
to soften the acrylic polymer particles so that they can fuse
together as the film dries. Many additives such as defoamers,
pigment dispersants and wetting agents also contribute low levels
of volatile organic compounds.
Q: What types of waterborne
acrylic coatings are commercially available for use on steel?
A: There are a number of different types of industrial coatings
available that are based on waterborne acrylics. Anti-corrosive
primers designed for direct application to prepared steel surfaces
are usually formulated with inhibitive pigments to aid in long
term corrosion protection. Topcoats are available in a range
of sheen from flat to high gloss. A special class of coatings
that are designed to act as both the primer and finish coat
are also available, as designated as DTM (direct-to-metal) coatings.
Elastomeric coatings are formulated to be applied as surface-tolerant,
thick film coatings which provide corrosion protection and flexibility.
Waterborne acrylic wash primers are meant to act as a thin film
tie-coats between substrates that are difficult for adhesion
(such as galvanized) and successive coats. Two-component coatings
based on acrylic/epoxy crosslinked systems are used for both
industrial maintenance and interior institutional coatings,
where greater chemical resistance is required.
Q: What is the temperature
and humidity range normally recommended with waterborne acrylic
A: The best temperature range for use of waterborne acrylics
is between about 60 °F and 90°F, although painting at
temperatures as low as 45°F can be done. Most manufacturers
recommend temperature ranges of about 45 to 110°F. Painting
at very high relative humidity (>90%) can lead to significantly
slower drying times. Usually it is recommended to paint when
the humidity is less than 85-90%, and the temperature is at
least 5 degrees above the dew point to prevent condensation.
Painting under conditions outside of the manufacturer’s
recommendations can lead to problems with film formation and
eventually performance. Click
here for more information on this topic.
Q: How long does a
waterborne coating have to dry before it can be recoated?
A: If applied within the recommended temperature and humidity
ranges, most waterborne acrylic coatings will dry and can be
recoated within 4 to 8 hours.