Brass is the term used for alloys of copper and zinc in a solid solution. Typically it is more than 50% copper and from 5 to 20% zinc, in comparison to bronze which is principally an alloy of copper and tin. Despite this distinction, some types of brasses are called bronzes.
Brass has a yellow colour, somewhat similar to gold. It is relatively resistant to tarnishing, and is often used as decoration.
Brass has been known to man since prehistoric times, long before zinc itself was discovered. It was produced by melting copper together with calamine, a zinc ore. During this process, the zinc is extracted from the calamine and instantly mixes with the copper. Pure zinc, on the other hand, is too reactive to have been produced by ancient metalworking techniques.
Bronze refers to a broad range of copper alloys, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminum, or silicon. It is strong and tough, and has myriad uses in industry.
When steel is excluded from the discussion, bronze is superior to iron in nearly every application. While it develops a patina, it does not oxidize. It is considerably less brittle than iron and has a lower casting temperature. (Steel, of course, has properties with which bronze cannot compete.)
Copper-based alloys have lower melting points than steel and are more readily produced from their constituent metals. They are generally about 10 percent heavier than steel, although alloys using aluminium or silicon may be slightly less dense. Bronzes are softer and weaker than steel, Bronze springs are less stiff (and so store less energy) for the same bulk. It resists corrosion (especially seawater corrosion) and metal fatigue better than steel and also conducts heat and electricity better than most steels. The cost of copper-base alloys is generally higher than that of steels but lower than that of nickel-base alloys.
Copper and its alloys have a huge variety of uses that reflect their versatile physical, mechanical, and chemical properties. Some common examples are the high electrical conductivity of pure copper, the excellent deep-drawing qualities of cartridge case brass, the low-friction properties of bearing bronze, the resonant qualities of bell bronze, and the resistance to corrosion by sea water of several bronze alloys.
Bronze is the most popular metal for top-quality bells and cymbals, and more recently, saxophones. It is also widely used for cast metal sculpture. Common bronze alloys often have the unusual and very desirable property of expanding slightly just before they set, thus filling in the finest details of a mould.
Bronze also has very little metal-on-metal friction, which made it invaluable for the building of cannons where iron cannonballs would otherwise stick in the barrel. It is still widely used today for springs, bearings, bushings and similar fittings, and is particularly common in the bearings of small electric motors. Phosphor bronze is particularly suited to precision-grade bearings and springs.
Bronze is typically 60% copper and 40% tin. Alpha bronze consists of the alpha solid solution of tin in copper. Alpha bronze alloys of 4-5% tin are used to make coins, springs, turbines and blades.
Commercial bronze (otherwise known as brass) is 90% copper and 10% zinc, and contains no tin. It is stronger than copper and it has equivalent ductility. It is used for screws and wires.
Bronze vs. Brass
1. Bronze is the familiar brownish color whereas brass is the more greyish greenish, bluish. Both will weather to the fine verdigris patina without maintenance.
2. They differ in the amont of metals used in the amalgam. Brass is a combination of copper and zinc while brass is a combination of copper and tin.
3. Bronze items are four times more expensive than brass.
4. Bronze is much stronger and more corrosion resistant than brass.
5. Bronze is harder and more abrasion resistant than brass
6. As brass deteriorates, it creates an oxide (a grey white powder - zinc oxide). Zinc oxide is acetic and will attack the lignum in wood. Once the lignum is gone the wood fiber is open to rot
7. Brass melts at lower temperature and therefore use less energy to melt. It machines and polishes much easier than Bronze and therefore the price to make a fitting from it is lower. Also, it goes away much more quickly and therefore the customer will have to purchase replacement parts much sooner.
8. Bronze is richer, more golden in color than brass which is usually a yellow color. If there is any doubt in your mind, try an easy test. Using the smallest drill bit that you have, drill a small hole in an unimportant area of the fitting and look at the metal turnings that come out. If they are long and stringy, the fittings are probably Bronze. If the turnings are small (like snow flakes), then the metal is probably brass and even more probably a leaded brass.