[AR] Re: Electroforming Experiment
- From: Ed LeBouthillier <codemonky@xxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sat, 13 Jul 2019 09:46:34 -0700
On Sat, 2019-07-13 at 16:30 +0100, Peter Fairbrother wrote:
Agitation is one way to control spikes and trees. But the best way is
to periodically reverse the current. What happens is that spikes do
form, then they are preferentially removed in the reverse phase.
I've used aeration for agitation. I hadn't gotten to reversing the
current (yet).
I use 1.6 seconds on, 0.4 seconds reverse, no gaps, same current
both directions, but ymmv. I am only getting a 60% overall rate -
effectively 1.2 seconds plating in 2 seconds - but as I can use a
much higher current, the overall speed of forming is faster.
Thanks for the insight and your experiences.
Some commercial people use ratios as low as 30% or so. Sometimes
they use gaps between phases, or higher currents in the reverse
phase. but the chemistry and math here is a) complex, it depends on
the bath chemistry, temperature, agitation, flow, rotation etc and
b) a lot of it is proprietary, so trial and error is probably the
best guide.
I've got a lot to learn, there's no doubt. But, this is the first step
toward where I need to go.
What bath chemistry are you using? "Acid copper" covers a multitude
of sins, from high-speed baths at > 300 g/l copper sulphate to high
throw baths at less than 60 g/l.
I used a basic 8oz Copper Sulfate + 8ml Sulfuric Acid + 1 quart
distilled water with a PEG leveler. Midas Bright was the brightening
agent.
This may not be optimal...at this point I'm not concerned with quality.
I'm just working on getting the set up, learning the process, and I
will improve everything moving forward.
This may not be where I end up, your insight is important on this
issue. But, I figured I could start with less-optimal chemistry and
learn and improve over time.
Temperature? Agitation? Flow? Rotation? Filtering? Chloride?
Temperature: about 110 F (45 C).
Agitation: aeration.
Flow? No...not yet.
Rotation: manually every hour or so.
I have a clock mechanism that I haven't yet applied to this.
Filtering: not yet. My initial bath was pure from the
beginning. Maintenance will definitely require more infrastructure
(e.g. pumps and filters).
Chloride: no.
There's so much literature to go through and sometime's it's
overwhelming about what direction to go.
Eventually, I plan on documenting the equpment, processes and materials
publicly so that others might be able to duplicate.
chambers for the SSME used:
5s forward 2s reverse
20C
5A/dm^2
187 g/l or 221 g/l Cu2SO4.5H2O
74 g/l H2SO4
chloride ion 81ppm by weight
xylose 0.3 g/l
Again, thanks for the insight.
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