Anti-corrosion selection for PV mounting fasteners should start with the corrosion class: hot-dip galvanizing suits inland C3; coastal/industrial C4–C5 calls for Dacromet or stainless natural.
Next consider structural load: load-bearing anchors prefer stainless or high-strength Dacromet. Finally total cost — stainless costs more upfront but is maintenance-free long term. FASTKING can supply salt-spray test reports to aid selection.