Crystal nucleus generation speed is fast, while the crystal nucleus growth rate is slow, then resulting large number of crystal nucleus, and resulting the crystal nucleus small, conversely is bigger. If the generation rate of crystal nucleus is faster than growth rate, coating file crystallition will be more micromesh and tightening. Cathodic polarization of increasing electrocrystallization can accelerate the growth rate of growth speed of crystal nucleus, then easy to form smaller crystals.
1. The cathode polarization method improving metal electrical crystallization:
Enhancing the cathodic current density: generally, the cathode polarization will increase with cathode current density increasing, while the coating film become more delicate at the same time. Under the circumstance of polarization increase with cathode current density increasing, the appropriate way to improve the current density will increase cathodic polarization.
2. To lower electrolyte solution temperature properly :
Lowering the temperature can slow down the cathodic reaction speed or ion diffusion rate and improve the cathodic polarization. In actual operation, for the negative impact of increasing the temperature can get up by increasing current density. The specific production operation, in the according to the actual temperature to adjust the electrolyte solution.
3. Add complexing agent:
Complexing agent is a substance which can complex metal ions in electroplating process. Complex ion is relatively simple ion on the cathode which difficult to restore, thereby increasing cathodic polarization value.
4. Add additives:
Additives adsorped on the surface of the electrode preventing the precipitation of metal, increasing the cathodic polarization.Cathodic polarization effect is not alwarys the bigger the better, when polarization over a certain range, will lead to a large number of hydrogen precipitation, so that the plating film becomes porous and rough. In production process, the situation is more practical, to take specify measures to increase metal crystallization cathode polarization effect.