Letter 12061

Silver Pulse Reverse Electroplating 

Hello! I have a problem I would like to better understand and manage. I would like to buy a Pulse Reverse Power Supply for my electroplating needs. This unit is able to provide a maximum voltage of 12 Volts with a maximum output of 20 AMP's when in DC mode, and a 40 AMP's maximum peak pulse current output when pulsing. I am interested in plating brass sheets, 0.14 inches thick. The brass sheets are 3.2" x 1.8" in size. That is a surface of 5.76 sq inches. Considering the sheets have two faces to be plated, we must double the surface. We'll then get 5.76 x 2 = 11.52 sq. inches. I would like to silver plate these sheets using the above unit. The problem is that I would like to know if this particular model will work. I am referring to its Ampere specifications (20/40). My goal is to be able to plate 5 (five) sheets at a time. Five sheets at a time would make a total surface of 11.52 x 5 = 57.6 sq. inches. That is an area of 0.4 square foot to be plated during each plating session. I would like to know whether this low-current unit will work ok for this area. Are the 20 AMP's in DC mode and 40 AMP's in peak pulse mode *ENOUGH* to plate the 0.4 square foot brass area with silver? Is this enough current for it? Please notice that I want to plate it in pulse reverse mode, not in DC mode - this is crucial! If you could let me know what you think, that would be great. And if you could detail a bit (IE: give me a formula or something to calculate the AMP's needed to plate a certain area) that would be even better. Thank you! Sincerely,

Dragos Alexandru
- Bucharest, Romania

You are doing the calculations correctly. The correct amps per square foot is often largely empirical, and in many cases if there is no pressure for a high production rate, the parts can be plated at a very low amps per square foot. Yes, a 20 amp rectifier is more than enough to silver plate a load of 0.4 square foot. A rule of thumb for rectifier sizing is 150 amps per square foot for chrome, 50 amps per square foot for bright nickel, and 40 amps per square foot is enough for rack plating anything else (one of the reasons I like to answer questions here, folks, is so I can learn something by people correcting me if I'm wrong).

You don't say why pulse reverse is crucial. It may well be, but it is usually one more complication, one more tricky variable to be tamed, and it strikes me as strange that someone who has not yet acquired any plating experience is absolutely convinced that something is crucial that the overwhelming majority of professional platers don't use.

Pulse reverse plating or not, I will be very surprised if you can silver plate brass sheets without intermediate layers of copper plating and silver striking.

 
Ted Mooney, P.E.
finishing.com Inc. - Brick, NJ

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