Types of corrosion cells. There are several types of corrosion cells operating on the principle of the difference in potentials of the cathode and anode regions. They are macro cells with electrodes visible to the naked eye or with a microscope, and a micro cell, invisible to the naked eye. Then macro cells occur, when the potential difference occurs due to the contact of two different materials, e.g.. two different metals (Fe i Sn). An example of a micro-cell is a cell formed due to the presence of various structures in the metal, e.g.. in two-phase alloys. A further example is a link formed at the grain boundary of a metal. The link also occurs due to e.g.. unequal machining of an object made of a given metal, when cold forging, bending etc.. due to differences in the structure of the metal subjected to deformation. So there, where there are contacts of different materials, multiphase alloys, metals with a fine grain structure and where the products are processed without annealing, there the corrosion will be more severe as a result of the action. local links. Uneven corrosion, occurring in certain areas of the surface of the metal object can be explained by the differences in the nature of the metal structure, the occurrence of stresses or inclusions in the structure of the material. The presence of cells can also be explained after finding, that the electrode potential is dependent on m. in. on the concentration of the electrolyte, that surrounds her.