Plating (Electroplating) is the principle of electrolysis in some metal surfaces coated with a thin layer of another metal or alloy of the process is the use of electrolysis of metal or other material attached to the surface parts of the process of a metal film which serves to prevent corrosion, improve wear resistance, electrical conductivity, and to increase the aesthetic reflective effect.
Work principle
To the plating tank plating requires a low-voltage high-current power supply as well as by the plating solution, to be plated parts (cathode) and an anode electrolysis apparatus. Wherein the plating solution composition varies depending on the coating, but contain metal ions provide the main salt, to complex metal ions in the main salt complexing agent forming a complex, to stabilize the pH of the buffer solution, the anode activator and special additives (eg brightener, grain refining agent, leveling agents, wetting agents, stress relieving agent and fog etc.). Plating metal ions in the bath under the action of an external electric field, the electrode reaction is reduced to metal atoms, and the metal deposition on the cathode process. Therefore, it is a liquid transfer including, electrochemical reactions and electrical crystallization step metal electrodeposition process....https://www.facebook.com/DongguanYizeMouldCoLtd?ref=hl
Filled with the plating solution in the plating bath, through a special cleaning and pretreatment to be plated as a cathode, an anode made of a metal plating, the poles of the DC power supply respectively negative and positive connection. Plating the plating solution containing metal compounds, conducting salts, buffers, pH adjusting agents and additives such as an aqueous solution of components. Energized, the plating metal ions in solution, under the effect of the potential difference to move to the plating layer formed on the cathode. An anode formed of a metal plating of metal ions into the solution, in order to maintain the plating of the metal ion concentration. In some cases, such as chrome, is the use of lead, lead-antimony alloy insoluble anode, since only the transmission of electronic, conduction current. The concentration of chromium ions in the electrolyte, the need to rely periodically added to the bath to maintain a chromium compound. Plating, the anode material quality, the plating solution composition, temperature, current density, power-on time, mixing intensity, the precipitated impurities, power supply waveform, etc. will affect the quality of coating, the need for timely control.
First, the plating solution has six elements: the main salt, the salt, complexing agents, buffering agents, anode activator and additives.http://www.aliexpress.com/store/502733
Plating principle contains four areas: plating solution, plating reaction electrode and reaction principle, the metal electrodeposition process.
The electrochemical reaction in the plating reaction: The figure is a schematic view of a plating apparatus, the parts to be plated as the cathode, the cathode is connected to the DC power supply, the metal anode coupling the positive DC power supply, an anode are immersed in the bath with the female. When an electric potential is applied between the anode and cathode, then the following reaction occurs at the cathode: electrode from the bath and the bath diffuses into the interface of metal ions from the cathode to obtain Mn + n electron, reduction to the metal M. On the other hand, occurs at the anode and the cathode opposite reaction that occurs on the interface anode dissolution of the metal M, the release of metal ions to generate n electron Mn +
Electrode and the reaction mechanism
A, electrode potentialhttp://www.aliexpress.com/store/502733
When the metal electrode is immersed in a solution containing the metal ions when, there is a balance of the metal loses electrons and the reaction mixture dissolved in the solution of metal ions and precipitation of the metal in the electronic reverse reaction should exist: Mn ne = M
Equilibrium potential of the nature and the metal temperature of the solution concentration. For accurate comparison substance to balance the potential of nature, it is required when the solution temperature was 250 ℃, metal ion concentration of 1mol / L, the measured potential is called the standard electrode potential. A more negative standard electrode potential of the metal are easy to lose electrons are oxidized, and the standard electrode potential value larger metal are easy to obtain electrons is reduced.
B, polarization
The so-called polarization refers to a current through the electrode, the potential deviation from the equilibrium electrode potential of the phenomenon. So, again the current - potential curve is called polarization curves. The polarization effect was mainly due to electrochemical polarization and concentration polarization.
1, electrochemical polarization
Since the electrochemical reaction rate is less than the cathode external power supply to the speed of electrons, so that the electrode potential in the negative direction of the movement caused by the polarization.http://www.aliexpress.com/store/502733
2, the concentration polarization
As liquid layer adjacent to the electrode sheet bulk of the solution concentration and the concentration polarization arising differences occur, said concentration polarization, which is due to diffusion of ions in the solution caused by the movement speed is less than e.
Plating metal ions in the bath under the action of an external electric field, the electrode reaction and the reduction of the metal atoms on the cathode metal deposition process.
Electroplating is simple terms, that is plated in the presence of salts want a solution to the matrix metal to be plated as the cathode, through the electrolysis, the bath in the plating metal cation want metal deposited on the surface of the base, the formation of deposits.
Plating elements: 1. Cathode: plated objects, refers to various connector terminals. 2. Anode: if soluble anodes, compared want metallization. If insoluble anodes, most of precious metals (platinum, iridium oxide). 3. Electroplating syrup: Containing For metallization ion plating syrup. 4 plating tank: can withstand, storage tank plating syrup, general considerations strength, corrosion, temperature and other factors. 5 Rectifier: providing DC power to the device.
(Polished → polishing) → → degreasing → washing hanging → (electrolytic polishing or chemical polishing) → pickling activation → (prepreg) → Plating → washing → (post-treatment) → washing → drying → → test under the hanging package
Plating the plating operation conditions refers to changes in the operation of factors, including: the current density, temperature, stirring and power waveforms.
Cathode current densityhttp://www.aliexpress.com/store/502733
Any plating bath has a get a good range of current density, to get a good coating, said minimum current density lower current density, maximum current to get a good coating density of said current density limit. Generally, when the cathode current density is too low, the cathode polarization is small, the coating of coarse crystal grains, rarely used in the production of a cathode current density is too low. As the cathode current density increases, the cathode polarization also increased (amount of increase in polarization value depends on a variety of different plating solution), are becoming crystalline coating delicate close; but the cathode current density is not too large, can not exceed the allowable upper limit (different plating solution under different conditions with different cathode current density of the upper limit), exceed the allowable upper limit, due to a serious lack of metal ions near the cathode The reason, the cathode will be generated and the projecting tip shaped like the branches of the metal coating, or generated on the entire surface of the cathode porous shaped like a sponge coating. Often encountered in the production of parts is likely to occur at the sharp corners and edges, "burning" phenomenon, in severe dendrite formation, or a sponge-like coating.
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