Cathodic behavior of platinized titanium electrodes under reverse current conditions in flow-through systems of the sea water electrolysis

Long-term tests and radiometric measurements of the corrosion rate of Pt an d platinized titanium electrodes (PTE) are carried out in sea water under c athodic polarization at the reversal of current. On the basis of these data and the results on the electrode-surface characterization and hydrogen sor ption by titanium substrates, it is shown that, at current densities higher than 0.8 kA/m(2), the main reason for the higher corrosion rates of cathod es as compared with anodes is the destruction of the platinum layer due to incorporation of cations of alkaline and alkaline-earth metals into their s urfaces. The corrosion rate of PTE serving as cathodes is much higher than that of Pt cathodes. The cathodic incorporation strongly depends on the cur rent density, electrolyte composition, and other factors and is localized a t defective sites and on surface areas operating under higher current densi ties at a nonuniform current distribution. It is shown that the titanium su bstrate is involved in the process of cathodic incorporation, and the hydro gen sorption in it increases. The formation and growth of a hydride interla yer impairs the adhesion properties of platinum deposits. It is found that the current reversal inhibits the cathodic processes of incorporation and h ydrogen sorption. It is shown that improving the quality of the substrate p reparation, manufacturing nonporous platinum deposits with regular structur es, ensuring a uniform current distribution on electrodes enhance the corro sion resistance of electrodes operating as cathodes at the reverse current modes. To ensure reliable operation of PTE under reverse-current modes, it is important to take into account a combination of several factors that, on the whole, determine the corrosion behavior.