|Go To Index
Named after its discoverer, Italian physiologist L. Galvani (1737 - 1798). Several stories circulate about the discovery. According to one version, Galvani became aware of the emergence of a current through a potential difference when the legs of a dissected frog, which he held up with clips made of different metals, suddenly moved. Elsewhere it is said that Galvani was dissecting the frog in the vicinity of an electrical generator and that is why the legs started twitching.
Galvanic current is electric current flowing between the electrodes of different metals that are immersed in an electrolyte solution. If several different kinds of metals are immersed in the solution, the current passes through all these metals. No liquid electrolyte is needed in a very humid atmosphere to give rise to a tiny amount of current that will form a galvanic cell.
This phenomenon explains why the solder joints of devices used outdoors are susceptible to interference. Potential may arise even on the welding seams of kitchen sinks made of stainless steel, resulting in galvanic corrosion, even if the welding wire is of the same material, because the structure of the steel sheet and the welding point may change. Tiny amount of current may also be the cause behind the corrosion of aluminum (Al-Zn-based) solders at the juncture of different metals. To prevent such corrosion, the joint must be covered with a protective plastic layer that prevents contact with water.