I made a argon plasma tube with 954 bronze aluminum bronze electrodes. After running for some time the anode (left) face is a silver colour. The cathode is on the right.
Does anyone know what this is? Is a deposit of some kind? Or has some reaction occurred with the aluminum bronze after being bombarded by electrons? Could this perhaps be the aluminum the aluminum bronze from the cathode being sputtered since aluminum has a lower melting temperature than the copper in the bronze?
In another set of electrodes of the same material the anode did not get a silver colour but instead just got discoloured dark burn marks.