At 11:14 PM 7/25/2003 -0400, you wrote: >Hi Ken, > >I was cleaning the electrodes after putting them through the abuse of >dealing with cabbage juice. They seemed to clean fine with isoprope and >H2O2. > >I looked at the darker electrodes under a 40X zoom microscope, and >noticed something funny. The surface was covered with tiny pits, but a >large portion was in the form of shiny islands. I assume the pits mean >silver is being liberated from those places, but why do the other areas >remain higher and shiny? ## No clue as to why but it's a well known event in the electroplating field. Since edges discharge more than flats, the pits should grow wider till they connect, then pit deeper. My best guess would be that once an ion is released, it establishes a pathway that sucks others off from right behind it until edge discharge becomes stronger than the pathway. I would guess that the added surface area in the pits actually lowers the current density on a given electrode and may even tend to distribute edge discharge away from the actual corners. I've found that used pitted electrodes give better results than new shiney ones if there are any marginal conditions present and since they are rough, any crap stuck to them sticks better. I recommend NOT shining the electrodes up with the green scrubby thingies. > >In calculating the current density, I assume the current is uniform over >the entire surface of the electrode. But now it seems that only 50% or so >of the surface is active. > >What would it take to make the entire surface active? ### A microscopic traffic cop? :-) [Ya got me] Even the big 20 and 30 pound electrodes in vigerously agitated electrolyte develop pits...pretty big naked eyes sized pits. If my pint sized memory serves after 30+ years of not being an electroplater, the pits are never deeper than they are wide. [seems like wider than deep in my old mental picture] Back then I never worried about current and numbers. Pull a sample and look at it..adjust current according to visual inspection of corners and holes..sometimes used bleed wires. Seat of the pants stuff.
BTW How one would expect to use Faradays equations to predict PPM when inevitable plateout is an unknown and an obviously highly significant amount of silver is a big question in my mind. Ode > >Best Regards, > >Mike Monett > > >-- >The silver-list is a moderated forum for discussion of colloidal silver. > >Instructions for unsubscribing may be found at: http://silverlist.org > >To post, address your message to: [email protected] > >Silver-list archive: http://escribe.com/health/thesilverlist/index.html > >List maintainer: Mike Devour <[email protected]> > >
