I need to polish gold and glassy carbon to mirror finish, which will be used as working electrodes in electrochemical studies.
I started from Grit 600, 1500, 3000, 5000, 7000 sandpapers, and then polished with alumina paste (1000 nm and 50 nm). After polishing with sandpapers, fine scratches were always visible and could not be removed by alumina pastes.
I tried to skip coarse sandpapers and started from 5000 or 7000 grit, but still resulted in the same fine scratches. What can I do to get rid of them?
What is the size of the surface of the gold electrodes that are to be polished?
When using "sandpaper" and other abrasives, loose grains generally get stuck on the extremely soft gold surface, or are even pressed into deeper layers of the surface.
With every grinding and every polishing process, the gold furthermore suffers deformations like foliation and folding on its surface. These surface defects (scatches etc.) can only be removed by etching.
This structure etching reveals the true microstructures like grain size, grain shape and grain distribution on the surface of the gold.
These microstructures can best be observed with a vertically reflected light microscope.
For further details please see our publication attached: Preparation methods....
This is link might be useful to your question.
https://zhuanlan.zhihu.com/p/343904342
gold is very soft, sand paper will leave some scratches.
polishing paste at a high speed may be better.