Plating is a technology which make the use of electrolytic to process the surface parts. When electroplating, the part in plating solution is negative, and metal ions under the action of DC power deposited the surface of parts to form a uniform, dense metal layer.
1,The necessary requirement for plating: external DC power supply, electroplating solution, electrolyzer constituted by plating workpiece and anode.
2, Electrolytic purpose: to change the parts’ surface appearance and physical and chemical properties, to acieve variety features of decorative, corrosion resistance, abrasion resistance, and other technical performance.
3, The crystallization of electrolytic process: the process of electrolyte metal ions or complex ions in the cathodic reduction to deposite metal coating called as electrolytic crystal.
Explain: Electrolytic crystal is an electrochemical reaction process, the metal ion is capable of reducing determined by cathode point . Only the cathode potential deviates from the equilibrium state, which produce certain overpotential will deposit metal crystal on cathode.
4. Metal electrodeposition is a complex process, which generally has several continuous stes or coincide interface reactions:
A. Metal ions in solution (such as Hydrated metal ions or complex of complexing ions) by mean of electromigration, convection, diffusion and other forms to arrive the near of of cathode surface .
B. Before reduction, the metal iron near by or on the cathode surface taking place of chemical conversion.
C. Metal ion gets electron from the cathode surface then reducts to metal atom.
D. Metal atom reach the growing point along the surface diffusion to reach growth point for crystal growth, or meet with other ions to form crystal nucleus and grow into crystals.
Explain: forming the metal crystals two steps: the formation and growth of crystal nucleus.