ELECTROLYSIS MODES VARIATION АS A UNIVERSAL METHOD FOR CONTROL THE ELECTROLYTIC COATING COMPOSITION

Abstract

The possibility of electrosynthesis and control of the composition of galvanic coatings by alloys based on metals of the iron group with refractory metals, in particular molybdenum, from a complex citrate electrolyte by varying the electrolysis modes has been proved. It has been established that coatings with a high oxygen content are formed by direct current, namely, more molybdenum oxides are fixed in these coatings in comparison with coatings used in unipolar pulsed electrolysis. In the latter case, the oxygen content on the protrusions and depressions is much lower and is respectively 21 at.% And 25 at.%. It was shown that during pulsed electrolysis, the content of the metal form of molybdenum is higher as a result of the reduction of molybdenum oxides with intermediate oxidation levels by hydrogen ad-atoms, which are formed in the partial cathodic reaction. The reduction occurs due to the spillover effect, the implementation of which is most effective during a current interruption. The formation of the oxide phase of inclusions directly during electrolysis without introducing it into the electrolyte as a second phase is justified. Depending on the completeness of this process, conditions are created for the formation of a metal coating from ternary alloys or metal oxide composites, the second phase of which consists of molybdenum oxides of an intermediate oxidation state, that is, a process is formed directly in the electrode. According to the results of atomic force microscopy, it was found that coatings synthesized in the galvanostatic mode can be classified as composite electrolytic materials, and the cathode deposit obtained as a result of unsteady electrolysis can be attributed to metal. The doped coatings obtained in a pulsed mode are characterized by lower porosity. The surface free energy for metal and composite coatings was calculated, the values of which are 127.74 mJ/m2 and 118.10 mJ/m2. When testing the electrocatalytic activity of Fe-Co-Mo ternary alloys in the reaction of electrolytic hydrogen evolution, high values of the hydrogen exchange current density were obtained both for metal and composite coatings.