MIL-HDBK-1110
cleanliness of hand-cleaned steel and power-tool cleaned steel.
Standard coupons of steel blasted to different levels of
cleanliness are also available for comparison from NACE, and
procedures for their use are given in NACE TM0170. Test kits for
detection of chloride, sulfate, and ferrous ions, as well as pH,
are commercially available. They contain strips, swabs, papers,
and operating instructions for simple chemical testing.
10.3.4
Profile of Blasted Steel. There are three methods for
determining the profile (maximum peak-to-valley height) of
blasted steel surfaces described in ASTM D 4417.
10.3.4.1 Comparators. Several types of comparators are
available for determining surface profile. These include ISO,
Clemtex, and Keene-Tator comparators. Basically, they use a
5-power illuminated magnifier to permit visual comparison of the
blast-cleaned surface to standard profile depths. Standards are
available for sand, grit, and shot-blasted steel.
10.3.4.2 Surface Profile Gages. A surface profile gage is an
easy instrument to use to determine surface profile, but 10 to 20
measurements must be averaged to obtain reliable results. The
gage consists of an instrument with a flat base that rests on the
profile peaks and a tip that projects into the valleys. The tip
can be blunted by dragging it across steel surfaces. This
prevents the tip from reaching the bottom of the valleys in the
profile, resulting in a profile value that is less than the
correct value.
10.3.4.3 Testex Press-O-Film Replicate Tape. Testex
Press-O-Film replicate tape produces the most precise profile
measurements, according to the precision statement of ASTM D
4417. The tape consists of a layer of deformable plastic bonded
to a polyester backing. The tape is rubbed onto the blast-
cleaned surface with a plastic swizzle stick to produce a reverse
replicate of the profile. The tape profile is then measured with
a spring micrometer. The micrometer can be set to automatically
subtract the 2-mil non-deformable polyester backing. After
measurements, the tapes can be stored as records of profile
heights.
10.3.5
Thermometers. Several different types of thermometer
and temperature recorders are available for field use. They are
used to measure ambient temperatures, surface temperatures of
steel, and temperatures of wet paints.
10.3.6
Psychrometers. Several different manual or battery-
powered psychrometers are available for measuring air
temperatures, relative humidity, and dew point. In most cases,
two glass thermometers are used with the instrument, as described
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