Phosphor bronze

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Phosphor bronze propeller salvaged from 1940s American warship.

Phosphor bronze (sometimes sold with the shorter name Phos Bronze) is an alloy of copper with 3.5 to 10% of tin and a significant phosphorus content of up to 1%. The phosphorus is added as deoxidizing agent during melting.

These alloys are notable for their toughness, strength, low coefficient of friction, and fine grain. The phosphorus also improves the fluidity of the molten metal and thereby improves the castability, and improves mechanical properties by cleaning up the grain boundaries.

Industrial uses[edit]

Phosphor bronze is used for springs, bolts and various other items used in situations where resistance to fatigue, wear and chemical corrosion are required (e.g., a ship's propellers in a marine environment). The alloy is also used in some dental bridges.

Grades A, C and E – C51000, 52100, 50700 are commonly used nonferrous spring alloys. The combination of good physical properties, fair electrical conductivity and moderate cost make Phosphor Bronze round, square, flat and special shaped wire desirable for many springs and electrical contacts and a wide variety of wire forms where the desired properties do not require the use of more expensive Beryllium copper. [1]

Phosphor Bronze (94.8% copper, 5% tin, 0.2% phosphorus) is also used in cryogenics. In this case its combination of fair electrical conductivity, and low thermal conductivity allows the making of electrical connections to devices at ultra low temperatures without adding excessive heat.[2]

Spent nuclear fuel overpack[edit]

The CuOFP capsule used as overpack for spent nuclear fuel disposal in the KBS-3 concept (Finnish version).

Oxygen-free copper can be alloyed with phosphorus (CuOFP alloy) to better withstand oxidizing conditions. This alloy has application as thick corrosion-resistant overpack for spent nuclear fuel disposal in deep crystalline rocks.[citation needed]

Musical instruments[edit]

Phosphor bronze tenor and soprano saxophones
Acoustic guitar string wrapped with phosphor bronze

Phosphor bronze is used in some metal wind instruments notably saxophones, and gives them a distinctive, reddish-orange hue, which can look different from the yellow-gold color of standard brass. Additionally, phosphor bronze is sometimes used in brass instruments (e.g., Flugelhorns), plus percussion instruments such as cymbals and snare drums. Some acoustic instrument strings for acoustic guitars, mandolins and violins are wrapped with this metal. Some harmonica reeds are made of phosphor bronze, such as those by Buckeye Music and the Suzuki Musical Instrument Corporation.[3]


Further increasing the phosphorus content leads to formation of a very hard compound Cu3P (copper phosphide), resulting in a brittle form of phosphor bronze, which has a narrow range of applications.

Around 2001, the Olin Corporation developed another phosphor bronze alloy[4] comprising:

Olin developed this new alloy for use in electrical and electronic connectors. When assessed in strictly metallurgical terms it is not true phosphor bronze, but a form of iron-modified tin brass.


  1. ^ "Little Falls Alloys". Retrieved 2009-05-08. 
  2. ^ "LakeShore". Retrieved 2011-12-23. 
  3. ^
  4. ^ "Innovations: Phosphor Bronze: Teaching an Old Dog New Tricks". Retrieved 2010-03-20. 

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