Chase cover replacement is a buy-once decision, if you make it correctly, because the failure that brought you here was a material failure, not a design flaw. Three metals compete; the comparison is short and decisive.
Galvanized steel: the incumbent that lost
It’s on your chase now because it was cheapest in 1994. The zinc sacrificial layer works until it’s consumed, single-digit years in our rain-heat cycling, after which rust runs unopposed: staining first, perforation eventually, framing leaks as the finale. Replacing galvanized with galvanized re-buys the same countdown at today’s labor prices. There’s no scenario where we recommend it.
Stainless steel: the default for a reason
No coating to sacrifice, nothing to rust, typically sold with a lifetime warranty, at a premium over galvanized that’s modest against the labor cost of any replacement. Every failure mode that killed your original cover simply doesn’t apply. For the overwhelming majority of DFW chases, this is the answer, spend the difference once, retire the problem permanently.
Copper: the statement piece
Everything stainless does, plus the patina, at a genuine multiple of the cost. It makes sense where the chase is visually prominent, and it pairs naturally with copper flashing on homes already committed to that aesthetic. Function-per-dollar, stainless wins; if the look is worth it to you, copper loses nothing else.