When two dissimilar metals are connected electrically and immersed in a conductive liquid, an electrolyte, their corrosion performance might differ significantly when compared with the metals, uncoupled. As a rule, the less noble material, the anode, is, more severely attacked, whilst the more noble metal, the cathode, is essentially protected from corrosion. This phenomenon is called galvanic corrosion.
If the passivity of one of the steel grades breaks down and corrosion occurs, the corrosion rate increases further by the galvanic coupling. In addition the galvanic series are dependent on temperature and the composition of the conductive solution. Knowledge about the series in the specific environment is necessary to predict galvanic corrosion.
Two different stainless steel grades in the passive state, coupled in an electrolyte, are quite close in the galvanic series and the risk for galvanic corrosion is less as long as the stainless steels remains in the passive state.
