Metallic Mil-Sec Coatings
Don’t Spray Like This
In spraying most mil-spec coatings topcoat colors our
painters get into a nice routine of spraying a certain way that brings us
satisfactory results. But there are a
couple of metallic colors in the Federal Standard 595 color deck that you can’t
spray the usual way at least without getting out-of-spec color appearance.
There are 650 colors currently in the 595 color deck. But 4 of those colors are metallics: 17043 gold, 17178 silver, 27043 semi-gloss
gold, 37200 flat silver. And one of
those colors, 17178, is used fairly often for aerospace coatings applications. If you spray 17178 like you usually spray Mil-PRF-85285
solid colors with 2 wet coats, you will probably think you have received a bad
batch of paint. This color in both Mil-PRF-85285
and in Mil-PRF-22750 has come up in more complaints than any other color. And upon further investigation the problem usually
comes from the improper spray techniques.
You can’t spray metallic colors the same way as you spray the rest of
the solid colors in the 595 deck.
Instead Spray Like This
Metallics must be spayed in 3 deliberately light passes with
the spray gun. Painters with
automotive paint experience have an easier time with these metallic colors
because they have had experience with spraying metallic paints during their
automotive careers.
Other keys to spraying metallics:
Proper mixing: Follow the
recommended mix ratio to the letter. If
allowed use some thinner as this will help to achieve better atomization.
Low fluid delivery: Lower your fluid
delivery to 1/2 to ¾ that you used for solid colors. Look for fine atomization to reduce mottling
& to bring out the metallic.
Multiple Passes: Start with light
tack coats, cross pattern (1.0-1.5 mils Wet)
Allow 1-5 minutes flash. Build film slowly with light coats, again
cross coating.
Do not allow film to get too wet.
(3.0-6.0 mils wet). To bring out bright
metallic fog the last coat from minimum 1 foot distance. Total DFT should be 1.5-2.0 mils for optimum
gloss and color consistency.
Consistent basecoat
or Primer color:
Always do original color match on the same substrate you’re your customer is
going to use. Gray primers impart
darkness and blueness, buff primer brings out yellow color.
Increased the distance
from object to be painted:
Painting too close with metallics will
cause mottling, edge pull, darker color.
Keep spray gun further back.
Agitate metallic
paints often:
Before mixing paint and catalyst, agitate metallic base component well.
After paint is reduced for spray,
swirl cup gun gently before each coat. Or
for large volume applications an agitated pressure pot is suggested.
