Copper + zinc. Copper + tin. Different properties.

Brass contains zinc which selectively dissolves in saltwater — called dezincification. Zinc leaches out leaving weakened spongy copper structure. Over time, brass parts weaken and fail. Bronze (no zinc, or small amount with tin protection) doesn't suffer dezincification. For any saltwater or chloride environment, specify bronze. For naval brass (C464 with tin added), some dezincification resistance but still inferior to bronze.

Naval brass (C464) is technically brass (zinc > tin in composition) but with 0.5-1.5% tin added for improved saltwater resistance. Middle ground: better than regular brass in saltwater, inferior to true bronze. Used in: above-waterline marine fittings, where cost matters but some saltwater exposure expected. Below-waterline or immersed: specify true bronze.

Bronze has excellent properties for plain bearings: (1) Lower friction against steel than brass. (2) Better wear resistance under load. (3) Tin content provides solid-lubricant effect. (4) Retains strength at elevated temperature. Leaded bearing bronze (C932, C954): lead content (5-15%) acts as additional solid lubricant. For bushings, gears, worm gear wheels running against steel, bearing bronze is standard.

Brass: bright yellow-gold, polishes to mirror finish, tarnishes over time. Bronze: reddish-gold with warmer tone, develops patina over time (often desirable for sculpture). For jewelry and bright decorative: brass. For sculpture and architectural: bronze. For aged/weathered appearance: bronze. Both can be lacquered to prevent tarnishing.

C360 brass contains 3% lead which acts as chip breaker during machining. Lead particles act as cutting fluid, produce clean short chips, enable fast cutting speeds. Machinability rating 100 (best reference) means: cuts 2-3× faster than steel, finer finish, longer tool life. Issue: lead is regulated (RoHS, environmental concerns). Alternatives: C370 (similar with less lead), bismuth brass (lead-free), silicon brass.

Brass generally cheaper due to zinc (cheap) vs tin (expensive). Free-cut brass C360: $6-10/kg. Bearing bronze C932: $12-25/kg. Aluminum bronze C954: $15-30/kg. Phosphor bronze: $15-25/kg. For cost-driven non-corrosion applications: brass. For marine or bearing applications: bronze worth premium. For decorative: either, specify based on appearance.