On 13/07/2019 23:21, Ed LeBouthillier wrote:
On Sat, 2019-07-13 at 20:38 +0100, Peter Fairbrother wrote:
So, I'm trying to summarize what I've read from you so far.
Here's the summary. Do I have this right? If so, this is what I'll work
towards.
ELECTROFORMING TECHNIQUE
=================================================
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.
Periodic reversal is particularly important for combustion chambers,
where organic brighteners and levellers are a no-no - they destroy the
high-temperature properties of the copper deposit.
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
Some typical baths, in g/l:
Normal:
CuSO4.5(H2O) 200 - 250
H2SO4 45 - 90
High Throw:
CuSO4.5(H2O) 60 - 100
H2SO4 180 - 270
Typical cathode current densities:
Normal - 2-7 A/dm^2 ( 0.129 to 0.45 A/sqin)
electrotypes (good agitation, continuous filtering): 20 A/dm^2
High current (cooled, very high agitation, PCR) - 50 A/dm^2
Anode current densities should not exceed the cathode density, or
5A/dm^2, whichever is larger.
Most additives mess up the high-temperature strength pretty badly,
even in tiny amounts.
