Bronze is primarily a metal alloy of copper and tin. The tin adds hardness to the copper and increases durability. Phosphor bronze includes the addition of up to 1% of phosphorous to the alloy. This addition improves strength, reduces the coefficient of friction of the metal and results in a finer 'grain'. The fluidity of the molten metal is also increased making this alloy easier to cast.
Just like pure copper metal (note green Statue of Liberty) and other bronze alloys, oxidation and stains can appear of the surface of the metal. This degrades the visual appearance required for certain part requirements. The electrical parts pictured below show tarnish, oxidation and water stains on the parts on the left.
Bronze Water Spots
The clean, bright parts on the right were vibratory tumbled with KP Ceramic Media and a solution of a mild acid cleaner, Kramco 1030. The mechanical action of the polishing media combined with the chemical cleaning of the compound resulted in a smooth, brilliant surface finish. This result was obtained in only 30 minutes of tumbling.