Although GALVALUME® steel sheet can be soldered, the presence of a thin film of
aluminum oxide on the surface makes soldering more difficult than when soldering
galvanized products. --more-- When soldering is necessary, the techniques and fluxes used to
solder aluminum should be used.
GALVALUME® steel sheet can be welded by conventional resistance and arc welding
processes. The safety precautions are similar to those for hot-dip galvanized sheet.
Because the surface contact resistance is low when compared with uncoated sheet,
resistance welding of GALVALUME® steel sheet requires welding currents, welding
times and electrode forces higher than those required for similar thicknesses of
uncoated cold rolled steel. These welding parameters are similar to those normally
used on galvanized steel. However, experience has shown that even more frequent
electrode dressing is required, as compared with galvanized sheet, to achieve good
There is less fuming when welding GALVALUME® steel sheet than when welding
galvanized sheet. The coating contains less zinc than a comparably thick galvanized
coating. Nevertheless, adequate ventilation is required to remove the zinc oxide
From a mechanical standpoint, any style of fastener suitable for use with sheet metal
can be used to join GALVALUME® steel sheet to itself or to other parts, provided the
fastener design is appropriate for the structural requirement of the application. The
list of acceptable devices includes common fasteners like nuts and bolts, screws and
rivets of all types, and special types like clamp fasteners, clips and blind screws.
Corrosion characteristics of the fastener material should be carefully considered from
two standpoints. First, the fastener should be equally as corrosion resistant as the
GALVALUME® coating to ensure long life of the fabricated product. Second, the
fastener material should be compatible with the coating; that is, it should be selected
to avoid accelerated corrosion caused by intimate contact between certain types of
Suitable fasteners include those made of nylon, other plastics or stainless steels, and
carbon steel fasteners with thick zinc alloy heads. Galvanized and other plated
fasteners are acceptable, but their corrosion resistance must be compatible with that
of the GALVALUME® steel sheet. Often, the plated coating on these types of fastener
is too thin to offer comparable corrosion resistance.
Fasteners made of lead or copper must never be used because they seriously reduce
the corrosion resistance of the GALVALUME® coating.
Adhesive bonding is a proven technique that can join steel effectively to many
materials. It can be used to provide special design capabilities that heretofore were
not possible. GALVALUME® steel sheet can be fastened readily by adhesive bonding
in the same way and with the same adhesives as hot-dip galvanized sheet.
Sealants are often used between overlapping areas of steel sheet to form watertight
joints and to achieve superior environmental durability. Neutral-cure silicone rubber
sealants are recommended for use with GALVALUME® steel sheet. These materials
need no primer. They are flexible and non-corrosive as well as resistant to heat,
cold, water and ultraviolet rays. In selecting a silicone rubber sealant, avoid those
materials that contain acetic acid or amines, which can promote corrosion during the
early stages of curing.
Other types of sealants, like butyl rubber and styrene butadiene rubber, also may be
As stated previously, U. S. Steel GALVALUME® steel sheet provides excellent longterm
durability. Therefore, unlike galvanized sheet which exhibits a longer life when
painted, the application of paint to the surface of GALVALUME® steel sheet is not
needed to achieve long term high performance.
If color is desired for decorative or aesthetic purposes, GALVALUME® steel sheet can
be readily painted either before prepainted steel sheet or after fabrication. For
prepainted product, the optimum types of paint line pretreatments and primers may
be different than those developed for galvanized product. The development of
technology related to coil-line painting of GALVALUME® steel sheet has evolved to
such an extent that prepainted GALVALUME® sheet is preferred by many customers
today especially for environments that involve aggressive corrosion.
When prepainted GALVALUME® steel sheet is properly coil-line painted and
rollformed, it has been shown to perform exceptionally well in the field. Issues that
were problematic during the initial 5 to 10 years of the product's use have been
solved as long as certain details of manufacture and use are obeyed. For example,
edge creep (undercutting of the paint coating along sheared edges) which was an
initial concern is no longer a problem. Similarly, staining at tension bends on the
rollformed panels is not encountered as long as the product is manufactured and
subsequently rollformed using prescribed paints and controlled bending during
One special precaution applies to prepainted GALVALUME® steel sheet. If the edges
of the rollformed panels are exposed to the environment during application (nonlockseamed
panels), the GALVALUME® steel sheet should not be side-trimmed before
painting. Good field performance requires that the edges be metallic-coated.
For painting after fabrication, the techniques used for painting galvanized sheet will
perform well with GALVALUME® steel sheet. Typically, painting after fabrication
requires cleaning to remove dirt and oils, treating to provide improved paint
adhesion and corrosion resistance. Consultation with paint suppliers who specialize in
the painting of metal is recommended.