MIL-HDBK-1110
Remember, answers are not always easily obtained in failure
analysis, and there may be multiple types and causes of failure.
Thus, one may in some cases have to be content with the most
probable cause or causes of coating failure.
11.4.1
Cosmetic Defects. The following paragraphs further
describe the cosmetic defects chosen in the initial decision.
11.4.1.1 Chalking. Chalking occurs only on exterior surfaces,
since it is caused by the sun's ultraviolet rays. The loose
chalk will be the same color as the coating, and, if it is
severe, an undercoat may be visible. Chalking should not be
confused with loose dirt which will not be the same color as the
finish coat.
11.4.1.2 Mildew. Mildew may resemble dirt but generally grows
in discrete colonies rather than being uniformly distributed. In
addition, it can be bleached with household bleach, but dirt
cannot. Also, it can also be identified microscopically by its
thread-like (hyphae) structures and its groups of spherical
spores. Mildew is usually black in color but some microorganisms
on coatings may have a green or red coloration.
11.4.1.3 Dirt. Dirt may be tightly or loosely held. It can
normally be removed by washing with detergent solution. However,
it may resist washing, if the dirt became embedded in the wet or
soft paint.
11.4.1.4 Uneven Gloss. Localized glossy spots may often be
detected only if observed from a particular angle. They occur
most frequently from spray application of heavy areas that do not
penetrate into wood or concrete/masonry surface.
11.4.1.5 Blushing. Blushing is a
defect from spraying fast-
evaporating coatings, particularly
lacquers such as vinyls and
chlorinated rubbers, on hot, humid
days. Condensation of
moisture on the wet film dulls the
finish to cause an
opalescence.
11.4.1.6 Bleeding. Bleeding occurs when solvent-containing
coatings are applied to a bituminous coating or pavement. The
stronger the solvent and the slower its evaporation, the greater
will be the tendency to dissolve the bituminous material and
cause it to bleed to the surface of the finish. New asphalt
pavements or toppings should be allowed to remain 4 weeks before
marking with paint to allow evaporation of volatile materials in
the asphalt.
170
Previous Page
