How to Paint Fiberglass by kesavilar


									                            How to Paint Fiberglass
Why paint fiberglass?
Fiberglass (Fiber Reinforced Plastic) is often susceptible to water incursion and/or sun damage
depending on the resin used. Epoxy weakens, with time, in sunlight. Polyesters are subject to
water infiltration and vinylesters are not as strong as epoxy; though are stronger than polyesters.
Water incursion will cause blistering or bubbling, though this typically takes years to
develop.However, once blistering appears its only a matter of time before the composite
(fiberglass and resin) delaminates and you have major problems on your hands. This is especially
important in boating.
Sunlight, usually with epoxy resins, will cause the composite to crumble. As you might imagine
this is pretty bad.

                                          HVLP Spray Gun
                                          Source: Liam Bean

Industrial Coatings
To add an additional barrier to both water and ultraviolet light (sunlight) paints are used (in the
business they are called industrial coatings) as a protective layer against these incursions. They
look good too.
In this hub I will recommend two types of paint (not brands) and cover the pros and cons of
using them.
With this information I'll also recommend two painting techniques. Any paint type covered here
can be applied with either technique.
This hub covers the basics of these methods. For full instructions on either look to the bottom of
this hub for links titled Roll and Tip Method of Painting and Spray Method of Painting.

Two Types of Coatings suited to FRP
There are two major categories of paint. They are both polymers (plastics based). One uses
exposure to air to cure; the other a catalyst, heat, and air.
Because these paint types are basically plastics in a volatile liquid they adhere well to epoxy
resin, vinylester resin, and polyester resin* as long as those resins are dry to the touch.
Basically any resin based paint is suitable for application on Fiber Reinforced Plastic (FRP), but
I recommend using epoxy based paints with epoxy based FRP resins and polyester based paints
on polyester based FRP. The reason is better bonding to the FRP.
However, should you be painting a boat or other FRP object subject to temperature extremes
and/or water immersion I recommend epoxy based paints regardless of the resin used in the FRP.
Epoxy, as long as it is protected from sunlight, is both strong and flexible. Naturally, the
pigments in an epoxy based paint will provide the ultraviolet barrier epoxy FRP needs.
* Listed in order of overall strength

What is in the Paint?
Paint typically consists of a vehicle (liquid), binder, and pigment. In paints used for durable
plastic coatings these are volatile organic compounds (liquid carrier),polymers (binder),
and pigment (color).
I do not recommend powder-coat due to the high temperatures required to bond the coating.
Since powder-coats require temperatures of 300~350F fiber reinforced plastics will melt.

Volatile Organic Compounds
A component of most of these paints is Volatile Organic Compounds (VOCs).
VOCs are liquids designed to evaporate at a set rate....usually quickly. The idea is for the liquid
to remain long enough for the paint to self-level, but evaporate quickly enough to present a
durable coating. VOCs serve as a vehicle for the paint pigment & binder and keep those pigment
particles in suspension until the paint is applied, self-levels, and dries. VOCs also insure faster
drying times.
Both one part polyurethane and two-part epoxy paints use VOCs. Without VOCs drying times
would be measured in days or weeks not hours. In some situations (professional shops) external
heat sometimes brings those times down to minutes.
As you might imagine anything that evaporates this rapidly is not good to breathe so proper
protective gear should be considered when applying these paints. A simple "hospital" style mask
is not appropriate as it allows VOCs to enter your lungs. A better mask is one designed
specifically for painting.

Another component in polymer paints is the binder.
Binders are the chemical compounds that cause the pigment particles to bind to each other. The
binder is typically a plastic including resins such as acrylics,polyurethanes, polyesters,
melamine resins, epoxy, or oil.
All of the coatings above work well with metal or wood. Only the bold faced types (above) work
well on fiberglass.
FRP is different because of it's typical uses of Fiberglass (FRP) and the additional protection
specific types of FRP require. Oil, melamine, and acrylics have too many disadvantages to be
effecively used on FRP.
Paints for FRP should not be oil based and melamine is not durable enough, to make a good
coating. Acrylics, polyurethanes, polyesters, and epoxy are best. Note that the pigment in epoxy
paint protects it from ultraviolet light. In matter of fact the worst thing for epoxy is direct
exposure to sunlight without some sort of protective coating.
When applying any of these paints there is very little difference in the two methods used in
applying them. Naturally, you want to read the manufacturers label carefully for any special
circumstances. Ambient temperature is the most common reason for differences in application
technique. Higher temperatures typically requires that a thinner or "brushing liquid" be added to
keep the paint from setting too soon. As you might imagine a paint that sets as you are using it is
bad news.
Paint technology has gotten so good that some car manufacturer paints make one big molecule
covering the car from front to back. Naturally, this makes a very durable coating. Automotive
paints are typically polymer based.

Pigments comprise the smallest percentage of a paint. Though certainly most modern pigments
are chemically derived, manufacturers tend to keep the actual sources and formulations a trade

Preparing the Surface for Paint
As with fiber-glassing, preparation is almost everything. Relative humidity should be below sixty
(60%) percent and temperature should be between sixty five (65°) and ninety (90°) degrees
Fahrenhiedt or 19° to 35° Celcius. Note that the lower the temperature (within the range) the
longer the drying time.
If the humidity is too high you'll trap water droplets in your paint and end up with a dull looking
finish. This cannot be buffed out and can only be "cured" if the offending layer is sanded out and
repainted. Worse, water droplets can migrate into your fiberglass can cause it to de-laminate.
In painting if there is too low an ambient temperature the paint won't harden. Too high a
temperature and the paint will set almost instantly.
Paint has to have time to "self-level." This means that any bumps, brush marks, or droplets left
by the spray gun or brush have to have time to level out and become smooth.
Surface prep is very important. Paint will not stick to oily or greasy surfaces. The oil from your
hands is enough to prevent adhesion. So a clean surface is vital. Also, if the surface is too rough
or has gouges in it those blemishes will show right through the paint.
Paint will not adhere well to glossy surfaces so sanding is also a vital step. This is especially true
of you are painting over a previous coating of poly or epoxy. The best bet it to use a very fine
"wet" sandpaper to be sure you have just enough roughness for the paint to stick.
Contrary to popular rumor you can paint a single part paint over a two part paint. It is not
advisable to attempt to paint with a "two parter" over a single part paint though I've had good
luck with this too. The key, of course, is preparation.
Rules of Thumb: If you are painting over;
    a fresh fiberglass or metal surface use a primer first
    a pre-primed surface, rough sanding (120 grit) first
    a first coat painted surface fine sandpaper (400 grit) first
    Succeeding layers wet sanding (1000 and higher grit)

The steps for painting with primer are not as rigid as the finish coats. By and large you can apply
primer a bit thicker and you certainly don't need a "tip" method to smooth it out. Primer provides
an excellent bond between fiberglass and the finish paint. It also provides an additional moisture
Be sure that each surface to be painted is clean and completely dry.
The typical steps to preparing the surface just prior to painting is to sand, blow or brush the
surface free of particles, denatured alcohol rub, water wipe-down, and a tack rag.

Paint Methods
There are two main methods of applying paint to various surfaces. These methods are geared
toward the home hobbyist or adventurous hobbyist depending on available equipment and/or
Note: You do not have to be a professional to spray paint, but if you've never done it before I
strongly advise practicing on something you don't mind throwing out. Even a scrap of
cardboard will do.
Spray: The paint is applied with a compressed air/or pumped pressure spray gun. This requires a
compressor and/or a good quality spray gun, paint filters, paint stirrers, eye and hand protection,
masks (you don't want to breath the stuff), solvents, containers, and plenty of clean rags.
I recommend compressed air and an High Volume Low Pressure (HVLP) gun. The advantages
are only low pressure (about twenty-five to fifty pounds) is needed. Since an HVLP gun applies
more paint that air, as the name implies, you'll also have fewer airborne particles to breathe.
You'll also get most of the paint on your target; not everything else.Note: paint settling on
objects not intended for paint is called "overspray." HVLP helps you prevent overspray.
      Spraying is quick and provides good, consistent, coverage with practice.
      Spraying can be done by one person
      Gives professional looking results
      Has reduced drying times
      Takes some practice to get it right
      Goes on thinly and so will take more applications for a good coverage.
      Lots of cleanup is required
      Risk of overspray (getting the paint on surroundings)
      Inhalation risk. This stuff can damage your lungs.
Roll and Tip: The paint is applied with a roller and then followed up almost immediately with
the tip of a fine bristle or foam brush. Tools requirements are a solvent resistant roller, solvent
resistant roller covers, brushes, containers, paint filters, eye and hand protection, stirrers,
solvents, and plenty of rags.
      Professional looking results (with practice virtually indistinguishable from spraying)
      Only a moderate level of skill required
      Less risk of breathing VOC fumes
      Fewer coats required (it goes on thicker than spray)
      Easier cleanup
      Takes longer
      Requires two people or one (very) fast painter
      Requires a sectional* approach
      Longer drying times.

* In this instance a "sectional approach" means rolling then brushing 3 foot square sections. This approach will prevent an area painted at the
beginning from drying before the brush "tipping" is applied.

Spray Painting Tools
Click thumbnail to view full-size
                                         30 gallon Air Compressor

Tools for Spraying
Refer to the photographs at right.

Tools required for spraying include;

    Air compressor and paint gun

    or piston sprayer

    Filters

    Paint (many brands can be sprayed or rolled)

    Thinner (depending on ambient temperature)

    Drying agent (depending on ambient temperature & humidity)

    Solvents (for "oops" and cleanup)

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