If the current density should exceed the limiting current density, a substantial hydrogen reduction reaction will occur. In such cases, the resulting deposits will be rough and granular, eg. burnt deposits. In a Hull Cell test, such roughness tends to appear on the left side of the test piece (side closest to the anode). This is because, as shown in p.16, the current concentrates to the left area, exceeding the limiting current density. In general, there are two ways to prevent burnt deposits: (i)to include additives in the plating bath or(ii)to set a high limiting current density. High limiting current density can be achieved by setting a higher Co (metal ion concentration), a larger diffusion constant D (higher solution temperature), and a smaller diffusion layer thickness d (stronger agitation) in Formula( 4 ). Limiting current density will increase by performing all conditions or even just one of the aforementioned methods.Therefore, by performing only a fast spray of the solution, it is possible to carry out the plating of the high current density. However, in actual fact, the bath-balance cannot be maintained for some solutions if the metal ion concentration or solution temperature is set too high. Also, with some solutions, the effect of additives weakens if it is agitated too strongly.

This Jet Plating Laboratory Kit can be used in order to confirm such a condition. There is“HCHS A-45” in the same kind of test equipment for high- speed plating. Whereas the test piece of Jet Plating Kit is fixed and the diffusion thickness is varied by spraying solution on it, the test piece of HCHS is rotated at a high speed. Please make good use of it together.