Theoretical justification of possibility of anode etching of the restored details of cars in sulfate electrolyte of galvanizing
Abstract
Theoretical justification of possibility of anode etching of the restored details of cars in sulfate electrolyte of galvanizing
Incoming article date: 13.03.2015Carrying out anode etching of details directly in working electrolyte of galvanizing will allow to reduce significantly time for preliminary preparation of the restored surface for sedimentation and to increase stability of results on ensuring quality of a covering. Anode etching represents electrochemical processing during which there is a removal of oxidic films, dissolution defective superficial a metal layer, revealing its structure. Thus on an anode surface the slime consisting of etching products is formed and ions of bivalent iron get to electrolyte. At achievement of a certain (critical) value of density of anode current the process of passivating of a surface, that is a surface covering a passive film which is followed by sharp increase of tension and decrease in current begins. There is a rough allocation of the small vials of oxygen clearing slime from an anode surface. The mechanism of anode etching of surfaces of the restored details of cars in sulfate electrolyte of galvanizing is similar to etching in the electrolytes containing sulfate ions that is as a result of process of formation of an oxidic film and parallel electrochemical dissolution by its anions. Quality of electroplated coatings of the restored details of cars zinc is provided with anode etching on necessary depth before emergence of steady passivation and the subsequent covering of a surface a continuous passive film. The mechanism of passivation of a surface of the anode in the electrolytes containing sulfate ions can be described by two theoretical models: 1) passivation is caused by protection of a surface an oxide layer of metal; 2) passivation is caused by special nature of adsorption of ions of oxygen. At achievement of anode density of current of a certain (critical) value, and change of active dissolution of a surface by the steady passivation which is followed by formation of a monomolecular passive film happens an electrode of a certain value of potential.
Keywords: anode etching, passive film, current density, adsorption, passivating, potential