Galvanic corrosion risk from fasteners?

This is a builder forum discussion, not a broad policy story, but it touches on a detail that matters if you're doing any exterior waterproofing or flashing work on your home. A homeowner asked about mixing metals near an entry landing: they'd waterproofed the area with a liquid coating, added galvanized steel flashing (called "bonderized"), and ran it up the wall over the sill plate and sheathing. Now they're choosing fasteners for a "weep screed" — the metal strip at the base of a wall that lets moisture drain out from behind stucco or siding — and wondered whether stainless steel screws touching that galvanized flashing could cause galvanic corrosion, where two different metals in contact speed up rusting.

Two experienced builders weighed in and said the risk is low. One pointed to a technical guide from a galvanizing trade group showing that standard corrosion charts overstate the risk, and said stainless fasteners should be fine unless the house is in a marine environment, where salt air raises corrosion risk generally. The other noted that in the telecom industry, stainless steel is actually used on purpose as a buffer layer between galvanized steel and other metals, specifically because it resists causing corrosion between them.

For most homeowners this is a reassuring, narrow technical point: pairing stainless fasteners with galvanized flashing is generally considered safe, mainly a bigger concern only in coastal, salt-air locations.