We studying in this research the reaction with Cadmium sulphate in an aqueous solution by physical - chemical method in presence of MaleicAcid , and determined compounds which are formed in this solution and we calculated of it formation the constants. After we used these electrolytes in plating by Cadmium , that is by electro precipitation of this metal on the solid electrodes (steel, copper) so that we definite the best of these electrolytes for galvany and the set necessary conditions for its use.