What About Galvanized?
Even when painted, galvanized parts can be expected to last only about 15 years according to the Sheet Metal and Air Conditioning National Association's (SMACNA) Architectural Sheet Metal Manual. A primary reason that Quick Mounts last so much longer – 50 years or more – is that the flashing and mount are aluminum while the balance of the hardware is stainless steel – both extremely corrosion-resistant metals that endure many years longer than galvanized parts.
The manual allows for, at minimum, 24-gauge galvanized steel "where the expected life of the roof is less than 15 years" but stipulates that the flashing must be painted as well.
No matter how old the roof is, the PV system will last at least 25 years, and probably longer. There is no good reason to use materials on a system you expect will outlast its own foundation.
SMACNA's manual lists the pros and cons of a range of flashing materials, including stainless steel, copper, lead, aluminum, and galvanized steel. Stainless is considered 100-year compatible, but is very expensive and relatively difficult to fabricate in the field. Copper and lead will last nearly as long and are easy to field fabricate, but they are expensive and toxic. Aluminum is considered 50-year compatible, is much less costly and non-toxic, but is still not as easy to field fabricate as galvanized steel, copper and lead. But since Quick Mounts are fabricated to the right size for you, you don't need to do any cutting on the roof.
Galvanized is cheap, readily available, and easy to fabricate at the job site. Unfortunately, the fine print in many roofing manufacturers’ instructions warn that using galvanized flashings may void their warranty altogether. If you must use galvanized for some reason, be sure to carefully read the roof warranty, as the difference between voiding it and keeping it intact can literally be a matter of millimeters. Some warranties, for instance, may accept galvanized flashing of 24 gauge while at the same time rejecting slightly thinner 26 gauge.
One more note on the use of galvanized steel: The Unified Facilities Guide Specifications for USACE (US Army Corps of Engineers), NAVFAC (Naval Facilities Engineering Command), AFCESA (Air Force Civil Engineer Support Agency), and NASA (National Aeronautics and Space Administration), forbid the use of galvanized flashings, as they do not have the life expectancy required to last as long as their roofs.
For more details, visit: www.smacna.org