Corrosion of permanent mould cast copper alloys in aqueous solutions

Abstract

Alloys cast using permanent moulds showed better corrosion resistance than those in the sand cast condition. Silicon bronzes exhibited high corrosion resistance while leaded tin bronzes showed the least corrosion resistance. The corrosion resistance of silicon brasses, silicon bronzes and low zinc yellow brass increased with added aluminium. The apparent activation energies for corrosion of silicon brass and leaded tin bronze were 25·5 and 12 kJ mol⁻¹, respectively, irrespective of the casting conditions. Rotating disc electrode data showed an increase in corrosion rates of silicon brass and low zinc yellow brass with increasing turbulence of flow of the solution. The amount of lead leached from the alloys during the 60th day of exposure to hard water in accordance with the test procedure specified in Section 9 of ANSI/NSF 61 was less than 10 ppb for all of the alloys studied with the exception of the silicon bronzes, for which values of up to 34 ppb were recorded.