What coating chemistry should I use?

By Gulf Coast Paints

Owners at Industrial Facilities often come to us wondering what type of
coating system is needed to protect their assets. Whether it is protecting steel
or concrete surfaces exposed to chemicals or concrete that needs a coating
or damaged concrete that needs to be repaired, we are often asked to come
up with a solution to protect their facility. With so many different options
available, it can be difficult to decide what is best for your facility. Here are
some different types of epoxies and urethanes that can be used in your

Epoxy Coatings

Epoxies have excellent adhesion to many substrates.
They’re known for being “surface tolerant” which is why so many epoxy
primers are specified. They can also be used as an intermediate coat and top
coat due to their durability and impact resistance. They generally have very
good chemical resistance which allows the higher performing epoxies to be
used for tank linings, containment areas, and for general protection against
chemicals. One of downsides of epoxies is that will eventually chalk and fade.
This is where Polyurethanes comes in to play, which we will discuss later.
Here’s some of the different types of Epoxy Coatings:

100% Solids Epoxy: These epoxies generally have very little or no Volatile
Organic Compounds (VOCs) and little to no odor. They can be used as a
primer, intermediate and topcoat depending on application. They can be
mixed with different aggregates for trowel downs to resurface concrete.
Another benefit is the use as binder to be mixed with metallic flakes, color
quartz, and as a base coat for color flakes. There is some downside to 100%
Solids Epoxies. They have a short pot life – generally 20-40 minutes and they
usually can’t be recoated until 6+ hours. (PC-1703, PC-1000, PC-1801, PC-
1803, PC-1850, CL-696)

High Solids Epoxies:  Most high solids epoxies provide excellent protection
against acids and alkalis. These epoxies can generally be used on steel,
concrete, and galvanized steel. Most H.S. epoxies have “fast cure” and “low
temperature cure” hardeners that allow for a high level of productivity in the
warmer months and the ability to cure down to cooler temperatures in the
colder months.   One of the most popular high solids epoxies is Amine Adduct
Epoxies. These epoxies are designed by having the curing agent with a small
amount of epoxy resin. (CM-15, PC-155, PC-275, PC-650)

Polyamide Epoxies: Polyamide Epoxies are one of the older epoxy
technologies that are still used today. Usually these epoxies are economical
and are used a primer and finish coat. They’re not as high performing
as the high solids and 100% solids epoxies but they offer a great solution in areas
where there’s no aggressive chemicals.  (PC-110, PC-145, PC-149, PC-200)

Cycloaliphatic & Novolac Epoxies: Both of these epoxies are very high
performing epoxies that are ideal for harsh chemicals. They’re great choices
for internal tank linings, secondary containment, pump pads, trenches, and
other high exposure areas. Most novolacs are designed to handle 98%
sulfuric acid and 37% HCL for splash & spillage.  (PC-517, PC-555, PC-590,
PC-1500, PC-1875)

Water Based Epoxies: Water Based Epoxies are great choices in less
demanding areas. They usually do not hold up as well against chemicals
some of the solvent based & 100% solids epoxies. One great benefit is that
these epoxies are usually low VOC and have little to no odor. Some common
applications for include control rooms, locker rooms, break rooms and
concrete flooring for light traffic. (PC-240)

Phenalkamines: Phenalkamine cured epoxies are excellent for low
temperature /cold weather applications. These coatings are fast setting, and
can be recoated the same day which is beneficial for owners and
contractors. Phenalkamines are usually lower viscosity than some of the other
epoxies, which makes it a great choice for line stripping in facilities. It has a
long pot life, great adhesion, and good chemical resistance. (PC-636)

Polyester Epoxies: Polyester epoxies are a very unique, two component
non-yellowing epoxy coating. They provide a hard, high gloss tile like finish
that has outstanding wash and scrubbability. It is ideal as an anti-graffiti
coating and has outstanding chemical and abrasion resistance. (PC-270)

Polyurethane Coatings

Polyurethanes are known for their outstanding UV
resistance, gloss retention and color stability. These coatings are usually sold
as finish and are usually applied at 2-3 mils DFT. One concern with
polyurethanes is their sensitivity to humidity and moisture. As a rule of thumb,
it is best to apply these coatings between 10 AM – 4 PM, which is when the
humidity is generally at its lowest point of the day. Depending on the product,
polyurethanes can have better chemical resistance and provide better
abrasion and impact resistance than the epoxies. Here’s some of the different
types of Polyurethane Coatings:

Moisture Cured Urethanes: Moisture Cured Urethanes are one component
urethanes that cure off of moisture and humidity. These coatings can normally
handle higher dry service temperatures than epoxies and two component
urethanes. They provide a hard finish that is very durable. Most MCU’s are
aromatic, which basically means they can change color over a period of time.
(MCU-100, MCU-101, MCU-104)

Acrylic Polyurethanes: Acrylic Polyurethanes are known for their excellent
gloss and color retention, UV resistance, and provides a tough and durable
finish. These coatings are used for exterior steel surfaces for long term
protection. Acrylic Polyurethanes are usually made with an aliphatic
compound which provides the long term stability needed in an Acrylic
Polyurethane. (CT-370, CT-371, CT-373, CT-380, CT-398)

Polyester Polyurethanes:  Polyester Polyurethanes is the premier
Polyurethane in terms of abrasion, scratch, impact resistance and have
excellent gloss and color retention. These coatings are made with 100%
Polyester resin which provides an extremely durable finish. Recommended as
finish coat for concrete floors in high traffic areas and exterior structural steel
surfaces.  Polyester Polyurethanes are a true C.R.U. (Chemical Resistant
Urethane), which makes it a great choice for aircraft hangars, service bay
floors and other high traffic areas due to its resistance to a wide range of
chemicals including salt, oil, gas, grease, skydrol, caustic, and most acids that
you may come in contact with your floor. (CT-332, CT-352)

CONCLUSION: Selecting epoxies and polyurethanes require careful
selection. The right choice can add longer service to your assets and prevent
you from having early failures.