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Re: gEDA-user: Lead Free at home?



On Monday 22 August 2005 06:15 pm, Dave wrote:
> On Mon, 22 Aug 2005, Marvin Dickens wrote:
> > On Monday 22 August 2005 05:49 pm, Dave wrote:
> > > I'm sorry.  The sulfuric acid spooked me.  Regarding the cool-amp
> > > recipe, where would you suggest I get the silver nitrate?  Most of the
> > > sources I find through Google and Froogle have it for roughly the same
> > > price as in the form of cool-amp.
> >
> > Well, on ebay at the moment, someone is selling 227 grams (1/2 pound) of
> > reagent grade silver nitrate. The high bid is $29.95 USD. You can find 
> > 99% ACS certified in the online stores on ebay for around $40.00 per 25
> > grams under the "Buy it now" deal.
> >
> > If you bought the 25 grams and added 50 grams of table salt plus 50 grams
> > of potassium hydrogen tartrate you would have 125 grams (4.41 ounces) of
> > of cloned kool amp for a total of about $42.00 USD. The price of kool amp
> > is $130.00 plus shipping and handling per 4 ounce bottle. This much kool
> > amp is probably a lifetime supply. OTOH, you could go the 227 gram route
> > and will it what is left of it to your grand children :)
>
> At http://www.cool-amp.com/New%20cool%20amp%20page.htm, a 4-ounce
> container is listed at $50.  This is what I meant with "roughly the same
> price".  That 1/2 pound of silver nitrate certainly looks nice.
>
> BTW, how far does an ounce of cool-amp go?

I don't know. I've never bought it - although, I've made it. This type of 
plate is really, really thin. As a comparison, a contractor grade garbage bag 
is 3 mills in thickness. With immersion, your guaranteed 2 mills and possibly
2.5 mills if the workflow is really good and there is no contamination. Rub on 
plating gives only a few molecules of thickness. 

Both rub on and immersion are what is know as self limiting because as soon as 
there is no exposed copper, the reaction stops. But, with immersion, the coat 
is applied in an extremely uniform system under more ideal circumstances than 
something being rubbed on (Immersion, like electroless and electroplating 
yields a very uniform plate).  

FWIW, 3 mills of tin or tin alloy plating can withstand 96 hours of continuous 
spraying with a saturated sodium chloride solution (Salt water) without plate 
breakthrough. 2 mills gives over 48 hours, but less than 65 hours. I would 
think that kool amp had breakthough within a matter of hours (Although, I've 
never seen any test data regarding rub on plating powders and solutions). 

As a side note, really thin plating is prone grow tin whiskers...

Back to your original quesiton, I would think that rub on plating probably 
goes a really, really long way because the plate is so thin. A 4 ounce bottle 
would probably last for years.

Best

Marvin

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