What Does Throwing Power Mean?
Throwing power is a measure of an electroplating solution's ability to plate to a uniform thickness over an irregularly shaped cathode.
Throwing power can be classified as good, medium or poor. If the irregularly shaped cathode's entire surface is plated to a uniform thickness, the solution has a perfect throwing power. Conversely, if it is plated only on areas near the anodes, then the solution has a poor throwing power.
Corrosionpedia Explains Throwing Power
In the electroplating process, the anode and cathode in the electroplating cell are both connected to an external supply of direct current. The anode is connected to the positive terminal and the cathode (article to be plated) is connected to the negative terminal. When the external power supply is switched on, the metal at the anode is oxidized and coated in cathode.
Throwing power is measured with a Haring-Blum Cell at distance ratio of 1:5 between two cathodes and an anode, plating at 2A for 30 minutes. The equation for throwing power is:
T.P.(%) = 100 (5 – M) / 5 + M – 2
Where T.P. is throwing power and M is the ratio of the weight of the deposited metals on cathodes.
To improve throw, a conforming anode may be fashioned to bring the anode closer to the low current density areas. This makes it possible to considerably improve the deposit thickness in areas with poor solution throw.