Effects Of Current Density And Etching Time On Etching Depth And Surface Roughness Of Ni-Cr-Be Alloy

Jeong, Seong Kweon; Jeon, Young Chan; Jeong, Chang Mo; Lim, Jang Seop

Abstract

The purpose of this study is to investigate which current densities and etching times will result in an optimal etching depth and surface roughness when an Ni-Cr-Be alloy is etched with 30% perchloric acid(HClO4 ). For this study,observations were made by means of an optical three-dimen-sional surface roughness measuring machine and a scanning electron microscope. The etchings took place under the following conditions using current densities of 300mA/cm2, 450mA/cm2, 600mA/cm2 and 750mA/cm2, and using etching time of three, five, six, seven and nine minutes. Under the conditions, the experiments reached the following conclusions. 1. When the current density is above 450mA/cm2 and the etching time is longer than five min-utes, the etching depth increased as the current density and etching time increased. And the surface roughness was significantly influenced by the interaction of the current density and etching time. 2. Under the etching conditions of 600mA/cm2 and five minutes, the optimal etching depth for a resin cement space and the highest surface roughness for mechanical retention were obtained. The etching depth and surface roughness were 32.86 micrometer and 7.90 micrometer, respectively. 3. Observations under the scanning electron microscope showed that both the corrosion at the grain boundary and the corrosion within the grain occurred on the etched surface. It was also observed that the corrosion at the grain boundary became more severe as the current density and etching time increased. In addition, at higher current densities and longer etching times, general corrosion appeared.