Hi Raja: It depends on the status of the electrode. If the electrode does not have a severe pitting or crevice corrosion, then you can do the cleaning mechanically, by using a graded sand-paper. You start with the coarse sand grade and finish with the soft grade sand paper. You can clean the electrode with acetone, followed with bi-distilled water, dry and it is ready to work with.
If the electrode has a deep pitting or crevice, then it is better to change with other electrode.
If your electrode is in a real bad shape covered by a thick layer that is hard to get ride of you can also dip it for a very short time in 10% HNO3. Just remember HNO3 also dissolve your copper (Cu+2HNO3-> Cu(NO3)2+H2(gas) )