Electropolish Copper

  • Take copper and use blue paper with brasso to polish the surface until you have a near mirror shine.

This breaks up the large process trenches on the copper surface and leaves small scratches and bumps that the more subtle electropolish can get rid of.

  • Prepare the electropolish solution by mixing the stocked 85wt% H2PO3 (Phosphoric Acid) solution with DI water in the ratio 8:1 (total volume can be adjusted depending on sample size.)

This high concentration ensures the solution gives enough ions to sustain a reaction consistently over the whole sample surface, otherwise you may find your solution can only sustain the correct voltage at a very high current (which will damage the copper). Because this uses a lot of acid the solution must be kept and re-used several times (it will turn blue as result of Cu2+ ion donation into the solutio - this may actually improve results as the Cu2+ ions may aid the mass-transport limiting polish step). Eventually the acid ions in solution will be used up and the solution must be replenished (normally after 5 polish cycles).

  • The best polish I have managed to get is at 1.8Volts, using a platinum counter electrode and a 3x3cm piece of brasso treated copper at the anode. Reports do show a large copper counter electrode maybe used in place of the platinum one, however I haven't managed to achieve successful results with this yet.

by Alex Ford