Many factors which affects the anode passivation during electrolysis were discussed in this paper. These includes the amount of slime and slime adhesiveness. The internal factors which affects the amount of slime include the type, concentration and the form of impurities which exists in the anode. The external factors include the concentration of the dissolved oxygen and the impurity ions in electrolyte or the electrolytic condition such as current density.
The anode impurities showed different behaviour of dissolution state according to the various forms of existence and the varying chemical properties of these elements or compounds. The anode slimes are formed either by dissolving of these impurities in the electrolyte at the anode or by remaining on the anode surface. The amount of these slimes greatly affects the occurence of passivation.
It was clarified that the coexistence of oxygen together with elements such as S, As and Bi in anode affects the amount of slime, adhesiveness and therefore also affects passivation. The possibility of passivation increased markedly with increasing current density, dissolved oxygen, impurity ions, as well as the concentration of H2SO4.
