hi tom!
really great method!
i wanted to ask if you may figure out the amount of hydrogen peroxyde consumed (and also if the etchant
was used very often which i assume or seldom. if one uses a soultion with H2O2 seldom (once a week or
so) i believe all of the H2O2 has vanished in between and needs replacement. the 10% you state for
initial use seems quite similar to the amount needed by my hcl h2o2 method. but interesting would be if
it is used up very quick, then it would become more expensive with less using rate.
i know you only adjusted it via etching rate but if you may remember at least one time, like after some
holydays or so, when you haven't used the bath some days if it needed the full 10%?
i'm also wondering if the copper also falls out when using hydrocloric acid and hydrogen peroxyde. it
never fell out in my etchant but maybe the concentration is yet too low (concerning only 35micrometer
copper thickness)...
also your description of electrowinning is very nice. that is exactly what i hoped for.
i'm wondering which reason there is for the lead plates?
why lead?
another question: you have obviously used stainless steel in your etchant, how did it resist?
perfect or was there some agression?
i see only one disadvantage of your method compared to the hydrocloric acid and this is availability of
sulphuric acid. it is much, much easier to get the hydrocloric acid here. it is sold in many stores, for
household use. sulphuric acid is only available in special stores. but if one needs hydrogen peroxyde he
has to go there anyways (if not getting it from hairdressing supply)..
i find your method very interesting but it would be more comfortable to stay with a hydrocloric
process... i will try if there also falls out the copper if i let it cool down.. (i always put the
etchant back into its bottle after useage, so it the copper concentration was diluted immediately).
many thanks, was a great help to mee.. also some satisfaction that somebody else thought of electrolysis
and did try it (even if it showed to be not comfortable).
regards
stefan
17.04.2003 15:54:12, "twb8899" <
twb8899@...> wrote:
>Why not try etching with a sulfuric acid and hydrogen peroxide
>mixture? We used this for years in a commercial shop with excellent
>results. The solution makeup is easy, 15% technical grade sulfuric
>acid, 10% hyrogen peroxide (35% grade), 75% water. This solution can
>be heated to 100 to 120 degrees F. and it's ready to use.
>
>One way to remove copper is to plate it out. This is called
>"electrowinning". Use lead plates for anodes and stainless steel
>sheets for the cathodes. The plated copper will peel off the
>stainless sheet if the edges are masked off with plating tape. The
>tape keeps copper from plating around the edges of the stainless
>sheet. After plating just flex the sheet and the copper peels off.
>
>My electrowinning tank had three lead sheets as anodes with two
>stainless steel sheets in between as cathodes. A 500 amp rectifier
>was used with the positive connection to the lead plates and negative
>connection to the stainless steel plates. A much smaller system could
>be made for hobby use.
>
>We transferred the solution to this tank on Friday afternoons and let
>it plate all weekend. On Monday we transferred the plated out
>solution back to the etching tank and started over. When using this
>method only the hydrogen peroxide had to be replenished to bring the
>etching rate up to speed.
>
>This seemed like a lot of work so after a while we went back to
>simply cooling off the working solution and letting the copper fall
>out. Copper will drop out as copper sulfate crystals when the
>solution is cooled to around 60 degrees F.
>
>We sold these crystals to a chemical recycler and never once
>generated any waste from this process. The same working solution was
>used for over seven years without replacement and etched many
>thousands of square feet of boards.
>
>All tanks, racks and hardware can be made of stainless steel, PVC,
>polyethylene or polypropylene plastic. Don't use nylon or delrin as
>they fall apart after a short time.
>
>I made all of our tanks from PVC plastic using a hot air plastic
>welding torch. My torch was made by Seelye Electric Company and was
>expensive but I see a direct copy of this torch being sold by Harbor
>freight for around $40. You also need a very small air compressor.
>The welding pressure used is around 2 psi or less. Air is used for
>PVC but nitrogen must be used for most other plastics.
>
>Analysis is by titration, however, in all the years we ran this
>process we never once analyzed the working solution. After dropping
>out copper sulfate crystals we just added some sulfuric acid and
>hydrogen peroxide until the etch rate was correct. We used a scrap
>piece of laminate and timed the etch rate. It was real easy to run
>this etching system with minimal problems.
>
>For a hobby system I would just use a plastic bucket and glass
>aquarium heater. When the solution is saturated the copper sulfate
>crystals will drop out and can be collected for resale or used as
>make up salts for a copper electroplating tank etc.
>
>Tom
>
>
>
>
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