MIL-HDBK-1110
9.6.7.5
Inspecting Concrete, Masonry, Wood, Plaster, Wallboard,
Old Paint. On these surfaces, specifications may have
requirements for measurements of moisture content and residual
chalk, as well as visual condition. The specification should
state how moisture is to be measured, since the different methods
provide different types of data.
Moisture content can be
measured either using a plastic sheet test (ASTM D 4263) or an
electric moisture meter. In the plastic sheet test, a piece of
plastic film is taped (all edges) to the surface. After 24
hours, the film is removed and the underside is examined for the
presence of condensed water. Prior to application of most
coatings, the sheet should be free of condensed water. This is
because accumulation of water at the concrete/primer interface
will usually lead to delamination of the primer. To use a
moisture meter on hard surfaces, small holes must drilled for the
electrodes. These holes should be repaired after the
measurements are completed. The contract should state a moisture
requirement. Residual chalk is usually measured using a piece of
cloth of contrasting color, in accordance with ASTM D 4214.
Other procedures are also described in ASTM D 4214. In the cloth
method, a piece of cloth is wrapped around the index finger,
placed against the surface and then rotated 180 degrees. The
spot of chalk on the fabric is compared with a photographic
reference standard. Chalk readings of 8 or more indicate
adequate chalk removal providing reasonable assurance that the
new coating should not fail because of application to a chalky
surface.
9.6.8
Inspect Coating Application. Proper application is
another essential factor in determining paint performance, and
the requirements of the specification must be followed. General
guidance on paint application is presented in Section 7 and SSPC
PA-1. Inspectors should assess ambient conditions, application
equipment, ventilation, mixing, film thickness, and drying and
curing conditions to ensure that they are within the limits of
the specification and the technical data sheets for the paints.
It is especially important that the paints be applied and cure
within the temperature and relative humidity limits of the
specification, since these conditions affect film formation. A
properly dried and cured film is essential for satisfactory paint
performance, and deviations from these limits may prevent proper
film formation. For two-component systems, the inspector should
ensure that the materials were mixed together and in the proper
ratio. For all materials, thinning should only be allowed in
accordance with the manufacturer's data sheet.
9.6.8.1
Application Equipment. Equipment to apply the coating
must be in acceptable working condition. When spraying, the
spray pattern should be oval and uniform, the gun should be held
at the proper angle and distance from the surface, and each spray
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