MIL-HDBK-1110
In making local repairs of damaged coatings, loose
paint should be removed by scraping with a putty knife before
lightly sanding or abrasive blasting any exposed substrate and
feather-edging existing sound paint to obtain a smooth transition
with the repaired area. Coats of repair material should be
extended 1 inch onto the surrounding sound coating.
4.4.1
Recommendations for Wood. Oil-based and waterborne
coatings and stains (frequently called latex) perform quite well
on new wood. A two-coat system, paint or stain, is normally
applied. However, as additional coats are applied to resurface
or repair weathered paint, the film thickness may become
sufficient to reduce the total flexibility to the point that
results in disbonding of the total paint system from the surface.
Thus, when topcoating or making localized repairs, no more
coating should be applied than necessary to accomplish the
desired goal.
Surface preparation of new wood normally consists of
lightly hand sanding or power sanding, carefully controlled so
that it does not damage the wood. Sanding is also appropriate
for preparing weathered surfaces for refinishing and for spot
repairing areas of localized damage.
4.4.1.1
Oil-Based Paints. Historically, wood has been
successfully painted with oil-based products that penetrate the
surface well. These coatings are very easy to apply.
Oil-Based Paint System for Wood
Surface
Preparation
Primer
Topcoat
Sand
one coat TT-P-25 or
one-two coats MIL-E-24635
MIL-P-28582
or TT-P-102
2 mils dft
2 mils dft per coat
4.4.1.2
Water-Emulsion Paints. More recently, latex coatings
have been found to be very effective in providing attractive,
protective finishes. They are also less affected by moisture
than are oil-based finishes and are generally more flexible and
thus less susceptible to cracking as the wood swells and
contracts with moisture changes.
A problem sometimes arises when repairing or topcoating
existing smooth alkyd coatings with latex paints. To obtain good
intercoat adhesion, it may be necessary to lightly sand the
existing paint and/or apply a surface conditioner containing tung
oil or some other oil that wets surfaces well before applying the
first coat of latex paint.
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