It should be noted that small amounts of anodic metals for the
three couples are detected on the surface of the cathodic metals,
suggesting that the dissolved anodic metal ions can diffuse toward
the cathode to be reduced partly. This deposition process may
decrease the potential difference between two metals, and thus
weaken the galvanic process. The significant fluctuation of current
observed for the Fe/Cr and Ni/Cr couples is probably related to the
fast dissolution of the anode Cr and to the stability of a Cr containing
layer formed on the cathode Fe or Ni. However, the
galvanic process is enhanced if the deposition is facilitated by
the formation of an insoluble alloy or compound (such as a carbide
with the cathodic material) [2]. The process can also be facilitated
if the dissolved anodic material can exist in several valence states
in the melt [2]. Sohal et al. [2] suggested that in case the oxidized
transition metal is multivalent, the cations can disproportionate at
the cathodic surface to form higher valence cations and the
element, e.g.: