Copper and Copper-Bearing Metal. Copper and copper-bearing metal
are particularly susceptible to solar radiation build-up. Allow for excessive
expansion and movement. Be cautious of galvanic action conditions.
General. The use of structural steel in a tropical environment has
been fairly successful when properly designed, protected, and maintained.
However, structural steel is only one of the many construction components that
requires a systematic maintenance program to provide economical service life.
It is unreasonable to galvanize significant quantities of structural steel.
Therefore, it is necessary to design systems that can be maintained over the
life of the project. Avoid concealed and inaccessible members. Paint exposed
structural steel for interior uses. For exterior uses, consider high-
strength, low-alloy steel. Avoid exterior bolted connections; continuous
welding with no voids is recommended. Consider epoxy paint systems or
elastomeric systems. Where possible, have structural steel shipped preprimed,
with prime coating touch up in the field.
Steel Exposure. Generally, for interior use standard structural
steel with a minimum coating system of a primer and one coat finish is
recommended. Ensure that the coating system is appropriate to the level of
corrosiveness of the environment. Also ensure that structural steel is
factory primed before being transported.
a) When structural steel is exposed to the weather and cannot be
subjected to a proper maintenance program (despite having been treated with a
coating system) avoid its use at all if possible. High-strength low-alloy
steel may be used in exterior applications if structural and economic
requirements justify its use.
b) In a tropical environment, with seawater mist, a coating system
for protection against the weather and corrosive elements is required. In
addition, consider galvanizing under the coating system in structures where
exposure to severe corrosion is anticipated.
c) When galvanizing is cost prohibitive, on steel members use two
coats of shop primer in combination with two finish coats. Surface
preparation includes sandblasting or mechanical brushing to near white steel
prior to paint application.
d) Where fasteners are exposed to the weather, specify galvanized
ferrous metals, stainless steel, brass, bronze, copper, aluminum, or other
corrosion resistant metals. In addition, consider the electrolytic action of
dissimilar metals in the selection of various metallic items, particularly
where concrete is a component. Do not use ferrous metal as finishing strips
or as components of other securement systems, even if a protective coating is
to be provided.