Final Fairing & Finishing - WEST SYSTEM Epoxy

atomized and overspray is eliminated, allowing you to work wherever temperature,
humidity and airborne contaminates can be controlled or at least tolerated.
Automotive finishes are limited to spray application, but most marine or architectural
coatings can be applied by spraying or by rolling or brushing. Marine linear polyurethane
(LP) systems require different catalysts for brushing and spraying. Additional reducers
and additives are available to control the rate of cure and other handling
characteristics.
Coatings are adjusted to the proper consistency for either spraying or brushing by the
addition of reducers or thinners. The amount of reducer/thinner added also affects the
film thickness and the rate of cure. They may also soften the surface of some substrates,
providing a chemical “bite” that improves adhesion. Reducers and thinners are blends
of volatile solvents. Coatings may contain more than 20% solvents, most all of which
evaporate into the air. Environmental concerns have restricted or will restrict the use
of many of the more hazardous paint solvents. The number of highly solvented coatings
is declining and the number of coatings with lower or safer solvents is increasing.
Selecting the right finish coating is becoming increasingly difficult given the changes
underway in the coating industries. Marine coatings, architectural coatings, automotive
and industrial coatings are all suitable for use over epoxy, although some will be
much more suited to an individual project than others.
Coating types
Finishing 19
At one time “paint” referred to a protective and decorative coating consisting of a natural
oil or resin binder and a solvent (together known as a vehicle), and pigments.
When the solvent evaporated, the oils hardened to form a film, with the pigments suspended
throughout. Although pigments have stayed pretty much the same, the natural
oil and resin binders have been replaced or modified by a variety of synthetic resins and
more complex film forming mechanisms.
Modern coatings offer a range of curing systems, handling characteristics and physical
properties, from water-based latex to linear polyurethane. As durability and protection
increase, cost, health hazards and difficulty of use often increase proportionately.
The following types of coatings are listed in order of protection they offer, although
physical properties can vary widely within each type. Coatings are commonly identified
by the chemical names of their resin/oil and solvent vehicles.
Waterborne coatings
Latex paint is the most common water-born coating and perhaps the safest and easiest
to use of all coatings. Latex paints are compatible with epoxy and they do an adequate
job of protecting the epoxy barrier from UV radiation. In many architectural applications
latex paint may be the most suitable coating to use.
The number of waterborne coatings is increasing rapidly. In response to restrictions on
volatile organic compound (VOC) emissions, massive research and development projects
are currently underway to improve the protection and durability of waterborne
systems. Water offers an obviously cleaner and safer alternative to the aromatics,
ethers, esters and aliphatics used as coating systems solvents. Newer waterborne coatings
include bottom paints, varnishes and top coats. They should be compatible with
epoxy, although few have been available to test for compatibility or durability.
Alkyd finishes
Alkyd resins are a synthetic polymer used as the base for a large family of coatings.
They are usually modified with natural oils like linseed, soybean, cotton, or sunflower
seed, or with other synthetic polymers like phenolics, acrylics or silicones. Alkyd finishes
are one part coatings that cure as a result of solvent evaporation. They have been
around for a long time and are among the lowest priced and easiest to use coatings.