Electrochemical and spectroscopic studies on dezincification of α brass: Part 1: Effect of pretreatment on surface composition of 70–30 α brass

The effect of various pretreatment procedures (degreasing with acetone, dry and wet mechanical cleaning with silicon carbide papers, acid and electrochemical cleaning, and use of a brightener) on the surface composition of 70–30 α brass was followed using X-ray photoelectron spectroscopy and Auger electron spectroscopy. Degreasing was applied to all surfaces before pretreatment and has no effect on surface composition. Dry mechanical cleaning with silicon carbide papers of grades 1000 and 800 resulted in surface zinc enrichment, while cleaning the surface with grade 320 paper maintained the bulk composition. In general, wet cleaning caused dezincijication. Polishing with a slurry of alumina resulted in a thin film of adsorbed alumina that masked almost all zinc and most copper. Cleaning with acids (HNO3, HCl, H2SO4)or acid brightener and electrochemical cleaning in H3PO4 caused surface dezincijication, except dipping for 5 s in 25 vol.-%HNO3, which did not affect surface composition. A combination of mechanical dry cleaning with grade 320 silicon carbide paper and dipping for 5 s in 25 vol.-%HNO3 is recommended as a pretreatment procedure for subsequent dezincijication mechanism studies.