The Effect of Cathodic Chrome Embedding in a Zinc Coating on Protection Properties

The effect of cathodic embedding chromium into zinc coating layers is analyzed from the standpoint of change in corrosion resistance. The zinc is deposited from electrolytes of various compositions on electrodes made of St3 steel grade. Grade TsO zinc is used as anode. The preliminary treatment of steel electrode involves treating the surface in the prephase potentiostatic embedding (PPD) mode at a potential 50 mV more positive than equilibrium zinc potential Eeq of the working electrolyte for 5 min. The zinc coating layer is deposited in potentiostatic mode at a potential of –1.20 V relative to the silver chloride reference electrode. The introduction of chromium into the electrodeposited zinc coating is made from electrolytes containing a trivalent chromium salt. The results of X-ray fluorescence analysis of the components of working electrodes after cathodic introduction of chromium, as well as the morphology of the surface formed, are explored using the scanning electron microscopy indicating the presence of chromium in the coating and its effect on the structure. The corrosion resistance of zinc coating layers modified through cathodic introduction of chromium at potentials of –1.05 and –1.10 V for 5 min is better than in chromated zinc.