MIL-HDBK-1110
in determining whether the exterior coatings are thermoplastic,
thermosetting, or bituminous. A cotton-tipped swab stick is
dipped in MEK or acetone and rubbed against the paint surface. A
thermosetting coating such as a vinyl which has been deposited on
the surface by simple solvent evaporation will redissolve in the
solvent and be wiped onto the cotton. A bituminous (coal tar or
asphalt) coating will also behave in this manner, but it will
impart a characteristic brown stain to the cotton. Properly
cured multiple-component thermosetting coatings such as epoxies
that cure by chemical reaction will not be affected by the
solvent. These solvents can also be used at the job site to
remove thermoplastic coatings to examine the condition of the
underlying substrate. The presence of mill scale may establish
the extent of surface cleaning. If rust is found, care must be
taken to determine if it was present before painting or resulted
from underfilm corrosion. Samples of the finish coat can also be
removed by sanding and taken to the laboratory for identification
as described in par. 11.3.6.
e) Once the various types of failure that may be
present have been identified, the extent of each type of
deterioration should be estimated. Standard block methods that
help to quantify the extent of coating deterioration are
described in ASTM F 1130, Inspecting the Coating System of a
Ship. Two sets of drawings are used to illustrate failures. One
set is used to identify the portion of the surface on which the
paint is deteriorated. The other set is used to identify the
level of deterioration within the deteriorated areas. For
example, a fourth of the surface could exhibit blistering and
within the areas 10 percent of the surface could be blistered.
11.3.6
Laboratory Testing. A more definitive laboratory
analysis of deteriorated paint is generally desired and may
become critical if the problem goes into litigation. Such
analyses require several representative paint samples to be
collected at the job site. Peeled and blistered paint is easily
sampled, but it may be necessary to obtain samples from sound
paint by scraping or sanding. Each sample should be placed in a
sealed container and properly identified and dated. Chain of
custody procedures (ASTM D 4840, Sampling Chain of Custody
Procedures) should be used if litigation is involved.
If samples of wet paint used on the job are available,
they can be tested by standard laboratory tests for conformance
to any SSPC, Federal, military, or State specification referenced
in the contract specification. If none of these standards was
167
Previous Page
