Investigation of cobalt sulphide coatings using the method of X-ray photoelectron spectroscopy

Regularities in the formation of cobalt sulphide layers (one cycle of the f ormation includes adsorption of Co ammoniates on the surface, hydrolysis, a nd sulphidation in Na2Sn (n=1-4) solution) and the composition of the coati ngs obtained have been investigated by the method of X-ray photoelectron sp ectroscopy. It has been determined that before sulphidation, i.e. after the stage of ri nsing-hydrolysis, in addition to Co(II) compounds (Co(OH)(2)) one can find in the coating the Co(III) compound CoOOH formed due to the action of atmos pheric oxygen, and water. Co(II) compounds dominate on the coating surface, while those of Co(III) do so in its depth. The sulphite found in the coating after sulphidation can be associated with a redox reaction 6CoOOH + 6S(2-) + 3H(2)O --> CoSO3 + 5CoS + 12OH(-) It is supposed that CoSOH found in the coating can be formed by two ways, i .e. in the course of CoS oxidation with O-2 and H2O to Co(III) 4CoS + O-2 + 2H(2)O --> 4 CoSOH or due to direct interaction of CoOOH with Na2S CoOOH + Na2S + H2O --> CoSOH + 2NaOH It has been shown that with increasing number of coating formation cycles a nd temperature of the solutions, as well as with aging the samples or formi ng the coating with a sulphidation agent with a longer sulphide chain - tet rasulphide (n = 4), the amount of Co(III) formed increases. All the components of the coating are supposed to be reduced to Co-o in the course of nickel electroplating on Co sulphide coating.