the present invention whether or not the cathode or cathode unit is removed from the cell this conditioning will include heating the cathode or diaphragm coated cathode unit is maintained at a temperature and for a heating time sufficient to substantially effect a change in the characteristic of any oxygen containing constituent present at the surface of the metal cathode or present in or on the diaphragm referring as representative to iron or steel as a substrate metal for the cathode cell operation as during shutdown or shutdown and subsequent restart may lead to iron corrosion products on the cathode which can result in the formation of magnetite fe 3 o 4 at this cathode surface such a cathode has been found to be associated with the deleterious generation of hydrogen in the chlorine product for a chlor alkali cell also with contaminated electrolyte cell operation even without shutdown may lead to the eventual presence of magnetite at the cathode surface this can be the case when deleterious quantities of iron contamination are present in the electrolyte it is to be understood that a combination of electrolyte contamination as well as iron corrosion may contribute to the problem continuing then with this representative iron cathode which.