Page 694 - Corrosion Engineering Principles and Practice

648 C h a p t e r 1 4 P r o t e c t i v e C o a t i n g s 649

FIGURE 14.29
Use of Tooke gage
for measurement
of paint layers.
(Courtesy of
KTA-Tator, Inc.)

The number and types of tests that can be conducted in the
laboratory are almost limitless. Table 14.9 lists some of the ASTM
tests relevant to protective coatings. Because field testing of coatings
is so costly in time, labor, and facilities, it has been the persistent aim
of formulators, raw materials producers, and users of coatings to
establish meaningful accelerated tests. These may involve a wide
variety of comparatively simple, as well as highly sophisticated
procedures.
These tests can define certain characteristics of a coating sys-
tem. This discrimination usually is specific to the type of acceler-
ated test, and frequently does not indicate in advance how a given
coating will perform in service. However, the tests are invaluable
when developing coatings or appraising new concepts in coatings
application or use.
General immersion tests: General immersion tests can be as simple
as the standard saltwater immersion test for coatings to be used
in the atmosphere, or as complicated as cold wall effect immer-
sion tests for heavy coatings to be used constantly in immersion
service. It is essential to reproduce the anticipated conditions of
the field exposure as closely as possible when evaluating coatings
for immersion service.