The reasons

1, the gas slowly released from the plating bath, plating solution began to disassemble, the gas not only on the surface of the plating release, but also in the entire plating liquid slowly and evenly released.

2, the rate of gas precipitation increases, the emergence of the above plating fluid, if not promptly taken effective measures, the gas escape rate will be faster and faster, will produce a large number of bubbles, so that the bath foam.

3, the formation of a black coating or sediment when many bubbles in electroless nickel plating solution, plating parts and the walls began to produce rough black coating, or produce many irregular black granular sediments in the bath.

4, bath bath in their own color fades in the decomposition process, plating color changing light, such as ammonia alkaline electroless nickel plating solution, when the self decomposition, plating color from dark blue to blue and white, at the same time also can smell a pungent odor of ammonia, the ammonia odor disappeared, electroless nickel plating solution has been completely decomposed.

The main factors

1, the proportion of plating fluid inappropriate
The hypophosphite (reducing agent) to improve the high concentration of hypophosphite concentration in plating bath, can increase the speed of deposition. But when the deposition rate reached the limit, continue to increase the concentration of hypophosphite, not only the deposition rate is not high, it will cause the self decomposition of plating liquid. Especially for the acidic bath, when the pH value is too high, the plating solution to decomposition of the trend of the more serious, the reason is: the high concentration of hypophosphite, electroless plating solution can be improved in more energy, but the chemical nickel plating is belongs to the liquid phase (bath), solid (coating) and gas phase (the precipitation of hydrogen) multiphase reaction system. When the plating solution is in the high energy position, it accelerates the tendency of the liquid phase component to turn to the solid phase and gas phase, which accelerates the reduction of the bath. If the plating solution at this time there are other unstable factors (such as local temperature is too high, there are turbidity, sediment, etc.), the most likely to induce self decomposition. When the concentration of plating solution of hypophosphite is too high, if the pH value is too high, it will greatly reduce the precipitation bath of nickel phosphite, and cause the work piece on the surface there are many granular.
The high concentration of nickel salt increase the concentration of nickel salt, when the pH of plating solution and high, easy to produce nickel phosphite and nickel hydroxide precipitation, so that the plating liquid turbidity, easy to trigger the self decomposition of the plating solution, and cause the work piece on the surface there are many granular.
The concentration of complexing agent is too low. One of the important functions of complexing agent is to improve the precipitation point of nickel phosphate in bath. The solubility and precipitation point of nickel phosphite solution in the bath solution are certain when the concentration of nickel salt, temperature and pH value are certain. If the concentration of complexing agent in solution is too low, with the process of electroless nickel plating, the phosphite will increase continuously, and the precipitation point of nickel phosphite will be rapidly reached, thus the phenomenon of precipitation will occur. These deposits will be one of the triggers for the plating solution itself, and one of the reasons for the many particles on the surface of the workpiece.
The pH adjusting agent concentration unchanged in the plating solution under the condition of other ingredients, if the pH adjustment is too high, is also prone to nickel phosphite and nickel hydroxide precipitation, and accelerate the decomposition of the reducing agent, the workpiece is caused by one of the many reasons on the surface.

2, plating solution preparation method is improper
The addition of hypophosphite too fast in the preparation of the plating solution, hypophosphite is not completely dissolved or too fast, will cause the hypophosphite concentration in plating solution of local high, will produce the precipitation of nickel phosphite.
The pH adjustment improper or high alkali too fast, or too much lye, will make the bath local pH value is too high, easy to produce nickel hydroxide precipitate, and the workpiece surface has many particles.
The plating solution is prepared in the order of improper plating solution is prepared, if not according to a certain order, such as pH value adjustment agent is added to the free complexing agent, reducing agent containing only nickel salt bath, not only to produce nickel hydroxide and precipitate in solution, and reduction of metallic nickel particles although the bath in precipitation, adding a complexing agent followed by cloudy and clear. However, a small amount of sediment exists, which affects the service life of the plating bath and affects the coating quality of the workpiece surface.
The preparation is not fully stirred in the plating solution is prepared in the plating solution, even if the pre made use of all kinds of drugs is completely dissolved, but in mixed, not fully stirred, compounds will produce naked elusive nickel.