Analysis of copper and zinc alloy surface by exposure to alcohol aqueous solutions and sugarcane liquor

Abstract

Copper and zinc alloys have applications in products exposed to harsh environments. Usually, these products have upon their surface a thin film of oxides, whose properties may change due to the exposure to air or aqueous solutions at room temperatures. This work analyzed copper and zinc alloy surfaces exposed to aqueous solutions of alcohol and a sugarcane liquor using mainly spectroscopic ellipsometry and confocal microscopy at room temperature. Using ellipsometry, oxide thickness was measured, either native ones or grown ones on the substrate exposed to air, and finally, those grown with the used solutions. Confocal microscopy was used to analyze the topography of the samples and measure their surface roughness in all processes. Besides, scanning electron microscopy with energy dispersion spectroscopy verified the composition of the elements present in the alloy, obtaining 70% Cu and 30% Zn. Surface roughness and oxide thickness were monitored by 29 days when the surfaces were exposed to air. Average roughness Ra varied from 0.165 µm (day 1) to 0.222 µm (day 29). Oxide thickness ranged from 4.755 nm (day 1) to 11.192 (day 29) in the same time interval when surfaces were exposed to air at room temperature. Roughness and thickness were also measured when the surfaces were exposed to aqueous solutions of alcohol and a sugarcane liquor at 1.5 h, 8 h, 24 h, and 48 h of exposure. The greatest variation for both average roughness Ra (0.232 µm to 0.76 µm) and oxide thickness (32.774 nm–68.105 nm) was observed when the surfaces were exposed to sugarcane liquor.