| The most popular steel substrates in the
metal roofing and siding industry are Galvanized and Galvalume. Galvanized substrates are
coated in zinc, while Galvalume substrates are coated with
an alloy of zinc plus aluminum. Both Galvalume and Galvanized are good
substrates for metal panels. With Galvanized substrates, the greater the amount of
zinc the greater the protection against panel corrosion.
Two commonly used Galvanized substrates are designated
as G90 and G60. These designations relate to the total
amount of zinc contained on both sides of the panel
surfaces. G90 contains 0.9 ounces of zinc for every one
square foot of panel while G60 substrates contain 0.6
ounces of zinc. The important fact to consider is that
G90 substrate contains 50% more protective zinc than G60
substrate. This difference will have a direct
correlation to panel longevity and long-term aesthetics
of your project. |
The coating system, or paint, for metal
panels is just as important as the substrate. For the
life of the panel the surface, or coating, will be
exposed to environmental elements - ultraviolet sun
rays, acid rain, dirt, etc. Over time, these
environmental conditions will break down the coating
resulting in panel fade and chalk.
Fade and chalk is not pleasing to the eye, and the
degree of fade and chalk is directly related to the
coating system. The most popular coatings for metal
panels are Kynar 500, Siliconized Polyester and
Polyester. Of the three, Kynar 500 coatings provide the
best protection against fade and chalk while Polyester
coatings provide the least protection.
| Chalking |
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|
| The white appearance is caused by chalking.
The silhouette is the result of tree leaves
rubbing chalk off the panels. The blue panels at
the far right are part of a building expansion and
represent original building color. |
| Fading |
|
|
| Partial removal of the sign indicates fade due
to ultraviolet exposure. |
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