This is Naval Bronze Alloy 464. (59% Cu/40% Zn/1% Sn) It is the same material that ship’s propellers are made of. For Hydrel, SWB application will be ocean environment such as dive tank, aquariums, pier, etc.
A salt water pool does not require SWB; Bronze (B) or Stainless Steel (SS) is sufficient. (Swimming Pools have 3 cleaning methods: Chlorine, Ozone, or Salt Water)