Rapid determination of corrosion rates of permanent-mold cast copper-base alloys*

CIM Bulletin, Vol. 90, No. 1009, 1997

M. Elboujdaïni and V.S. Sastri, Materials Technology Laboratory — CANMET Ottawa, Ontario, Canada

Corrosion rates of silicon brasses, highzinc yellow brass, low-zinc yellow brass, leadedtin bronze and silicon bronzes in both permanent-mold and sand-cast conditions were determined in soft water of pH 3, 5 and 8, and hard water of pH 8 at 70°C by electrochemical polarization technique. The alloys in permanent mold condition showed greater corrosion resistance than sand-cast condition. Corrosion rates obtained from weight loss measurements showed no observable trend of a difference between permanent-mold and sand-cast alloys. The corrosion rates decreased with increasing pH of the medium. Silicon bronze and silicon brass showed high corrosion resistance while leaded-tin bronze showed the least resistance. Addition of small amounts of aluminum improved the corrosion resistance of silicon bronzes and silicon brasses. Alloys in permanent- mold condition showed greater resistance to dezincification than sand-cast alloys when average pit depth parameter is considered.

Keywords: Metallurgy, Corrosion, Copperbase alloys.