FIRE-RESISTANT (INTUMESCENT) PAINT
A relatively new (literally space-age) develop-
ment is truly fire-resistant paint. This intu-
mescent paint expands tremendously when
exposed to the great heat caused by a fire.
First created for use on Apollo spacecraft
reentry vehicles, it is now available in a num-
ber of varieties from several paint manufac-
turers, such as International Paint/Interna-
tional Protective Coatings (Chartek). These
paints are in common use on offshore oil
platforms and in the machinery spaces of
large ships. Paints such as these do notserve
as insulation until there is a fire, but they add
a considerable range of added safety should a
fire occur.
In most average boats of steel or alu-
minum construction, an intumescent paint un-
der the insulation of drystack exhaust systems
(in exhaust trunks and such) is probably not
justified. On fiberglass and wooden vessels, it
will add a significant margin of safety to paint
the inside of the exhaust trunk with an intu-
mescent paint first before installing the usual
and still required insulation. Again, such intu-
mescent paint does notreplace the usual re-
quired insulation or lagging, and it is not used
on the exhaust pipe itself. It is for added pro-
tection of the structure.Painting the Exhaust Pipe
If the exhaust pipe is polished stainless, it can
be left unpainted, but a standard structural-
steel exhaust pipe must be painted for pro-
tection as well as appearance (on the out-
side). International Paint’s (International
Marine Coatings) Intertherm 50 silicon alu-
minum paint is one good product for this ap-
plication. It’s rated to 1,000°F (540°C) and
specifically listed for applications on exhaust
stacks. It comes only in a silver/aluminum
color.
POR-15, Inc., makes POR-20, a silver
paint, and Factory Manifold Gray (gray, of
course). Both are rated at 1,400°F (760°C).
They also produce Black Velvet, rated at
1,200°F (650°C). All three are suitable for
exhaust-stack-pipe paint. POR-15 also pro-
duces engine enamels in a wide assortment
of colors suited to painting engine blocks, but
not rated hot enough for exhaust pipes.
If you want a larger assortment of colors
(and you aren’t using polished stainless pipe)
one source is automotive “header” paints,
such as from VHT Paints (www.vhtpaints.
com). These coatings come in many colors
and are rated at over 1,300°F (700°C). VHT
also makes manifold coatings rated as high asPART THREE:EXHAUST SYSTEMS
Figure 9-22.
Alternate trunk
insulation