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  • Increase of technological reliability of preparation of details of mobile equipment for galvanic sedimentation of zinc coverings

    Zinc electrodeposits gained the distribution generally thanks to high protective properties. However it is possible to apply zinc electroplated coatings and at restoration of worn-out surfaces of details of cars. Thus zinc electrodeposits possess the high durability of coupling with a substrate that is pledge of long-term service of the details restored by zinc. Ensuring high durability of coupling of zinc electroplated coating with a basis possibly only at careful observance of technological process of preliminary preparation of a surface for sedimentation and directly the sedimentation. Some researchers suggest to estimate the received durability of coupling of a covering with a basis from the point of view of the theory of reliability. Technological reliability of process of preparation of details for galvanizing is meant as percent of the restored details, with a high durability of coupling. Process of preparation represents technical system in which operations act as elements. Reliability of technical system are defined by quantity and reliability of elements, their functional communication. And reliability of elements, is defined by technology factors and depends on quality of carrying out the previous operation. Refusal of any of elements causes refusal of all technical system. That is communication between elements of system consecutive and it is possible to apply the second theorem of probabilities according to which the probability of joint emergence of several dependent events is equal to work of probability of one of them on conditional probabilities of all others to it. It is necessary to understand change of reliability of an element in time as stability of reliability. For the purpose of improvement of technological process of galvanizing it is possible to perform operation of anode etching directly in galvanizing electrolyte. Thus the block diagram of preparation of a detail can be submitted as follows: machining; degreasing of surfaces of a detail Vienna lime; washing in cold water; anode etching galvanizing electrolyte; removal of products of etching from the covered surfaces and an exit to the mode; galvanizing.

    Keywords: case detail, restoration, repair, defect, resource way of restoration, car repair production

  • Theoretical justification of possibility of anode etching of the restored details of cars in sulfate electrolyte of galvanizing

    Carrying 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

  • Theoretical justification of increase of productivity of galvanic sedimentation of coverings on the restored surfaces of details of cars

    Increase of productivity of processes of sedimentation of coverings on the restored surfaces of details of cars without decline in quality of the received deposit is a main objective on the way of improvement of galvanic processes. Productivity of galvanic sedimentation depends on the size of potential of the cathode and the anode; from concentration of components of electrolyte about a surface of sedimentation (cathode); from uniformity of delivery and dispersal of ions of metal on a sedimentation surface; from quantity of active sites of the cathode; from nature of passivation of the cathode; from temperature of electrolyte and from the speed of the movement of electrolyte in prikatodny space. Very strongly passivating of a cathodic surface limits the possible growth of productivity of galvanic sedimentation. Passivating consists in education on a surface of the cathode of the continuous passive film consisting of hydrogen, products of reaction of metal with electrolyte components, oxygen of air and foreign inclusions. The passive film is almost insoluble and disturbs electrocrystallization process, shielding a cathodic surface. And cathode covering speed a passive film directly depends on density of cathodic current. It is possible to assume that at achievement of some value of density of cathodic current the speed of formation of a passive film will exceed, the speed of delivery of ions of metal to a cathodic surface and origin of crystals of the besieged metal will become impossible. And on the remained active sites of the cathode where the passive film is absent or has the smallest thickness and growth rate, there will be centers of growth of crystals of metal (dendrites) on which there will be a concentration of the main processes of electrocrystallization. That is the cathodic surface of the restored detail will become covered by the local centers of sedimentation of metal – dendrites. The passive film interferes with growth of limit density of cathodic current at which receiving qualitative electroplated coating is possible. Mechanical elimination of a passive film during sedimentation of a covering considerably facilitates process of electrocrystallization and formation of a layer of metal on the processed detail surface, provides increase of uniformity of the received layer of metal and its microhardness, and also will prevent active formation of local sites of growth of dendrites at the high density of current.

    Keywords: passive film, adsorption, sedimentation productivity, electrocrystallization, mechanical activation, crystal lattice

  • Experimental installation for laboratory researches of galvanomekhanichesky sedimentation of zinc from flowing electrolyte on the restored surfaces of details of mobile equipment

    Improvement of technological process of galvanizing in flowing electrolyte without decrease in its reliability and quality of the received deposit can be carried out by carrying out anode etching of the processed surface directly in the main electrolyte of sedimentation. And, providing such conditions of anode etching at which, the details which are formed on a surface products of reactions easily are removed a channel of electrolyte is possible. For the purpose of identification of extent of influence of technology factors on anode dissolution of the processed surface it is necessary to conduct elektrokhikmichesky researches. The installation including electric was for this purpose developed and made and gidravklichesky speak rapidly. The Elektkrichesky part contains power-supply circuits of an electrolytic cell to the asymmetric variables odnopoluperiodno straightened, dvukhkpoluperiodno straightened by current and straightened by current with the lowered pulsation, and also a chain of heating of working electrolyte. The hydraulic scheme of experimental installation includes: the kisloktostoyky electric pump, pipelines, filters, the device for an electrolytic precipitation of coverings and a bathtub with electrolyte. Electrolyte in a cell moved by means of the electric pump. Giving changed in steps, due to change of diameter of the section through passage of the giving pipeline by means of replaceable inserts. Authors of the device for electrolytic drawing coverings are Zakharov Yu.A. and Spitsyn I.A. (patent No. 2155827). The design allows: to increase the speed of a channel of electrolyte; to carry out activation of the cathode, using energy of a channel of electrolyte; to increase the accuracy of copying of the cathode the activating elements; to use higher density of current and to reduce power consumption of the device. Electrolyte, in the course of sedimentation, was constantly filtered. As filtering material used fiber glass. The filter if necessary it is possible to dismantle and wash out quickly. Such filtering element slightly interferes with a channel of electrolyte, is simple in service, is cheap and quite sufficient. Thus, the offered design of experimental installation allows to conduct necessary researches of process of sedimentation of a zinc electrodeposit for its improvement.

    Keywords: case detail, restoration, repair, defect, resource way of restoration, car repair production