Soldering terminology

If metal or an alloy is immersed in an electrolyte liquid and the metal, the alloy or the liquid is non-homogeneous, local electrodes (anodes or cathodes) may arise between which current flows, forming a galvanic cell. These tiny cells are called local cells. If, for example, a solder joint is exposed to liquid electrolyte, processing cracks in the solder alloy, internal mechanical stresses or irregularities in the composition, temperature or pressure of the solution to the formation may lead to the formation of local elements and thus lead to the corrosion of the solder joint. Besides the actual chemical reaction, corrosion of solder joints on contact with rain drops (particularly in acid rain) may also be caused by local cells. However, this phenomenon should not be confused with galvanic current. See also Galvanic current.