kilowatt
Hazard to Others
Posts: 322
Registered: 11-10-2007
Location: Montana
Member Is Offline
Mood: nitric
|
|
Electrolytic Alloy Deposition
Electrolysis in various fused salt baths is effective at depositing heavy layers of most metals from an anode consisting of the metal onto a cathode
substrate. The process proceeds as the anode is oxidized and the oxide dissolves into the melt, where it is reduced to metal at the cathode.
I would like to use a process like this to form solid alloy stock or deposit layers of alloys onto other parts. The problem is that if I started out
with an anode made of the alloy itself or added salts to the electrolyte corresponding to the alloy composition, they would plate out at different
rates. It would take a great deal of experimentation to determine the different rates at which the metals are deposited, and compensate by adding
additional material so the electrolyte does not become enriched with certain metals over others.
My idea is to use several anodes in the form of flat bars each consisting of a pure metal being a constituent of the alloy. These would be arranged
around the cathode, which would be spun to achieve radial uniformity of the deposit. To account for the difference in deposition rate (which would
still require some experimentation), the bars would be of different widths, but would all be lowered into the melt to the same depth to ensure
longitudinal uniformity of the cathode deposit. Current could be monitored for each anode to ensure it is being dissolved at the proper rate, but I
believe each anode would have to be connected to the same voltage source to avoid them plating from one to other. It might be possible to use anodes
at different depths if there was some kind of vigorous vertical stirring of the electrolyte (possibly with ceramic impellers, gas bubbling, or induced
convection by a cooler). This would allow better control over the dissolution rates by adjusting the depth of each anode.
[Edited on 30-3-2009 by kilowatt]
The mind cannot decide the truth; it can only find the truth.
|
|
|
chief
National Hazard
Posts: 630
Registered: 19-7-2007
Member Is Offline
Mood: No Mood
|
|
This usually is done by variation of the voltage, and in water-solution baths. Eg. bronze may be deposited like this, other alloys as well. The key is
that when increasing the voltage one metal deposits first; further increasing the voltage then leads to deposition of the second metal as well.
Thereby the ratio of 2 metals can be deliberately set; usually some alternating current from a functio-generator (amplified) may be used for that ...
.
Of course the conc. of the salts in the bath must be low enough for the voltage to be able to rise to the values for the higher depositing materials.
By varying the concentrations of the salts in solution at least a third metal should be possible; with more it probably will get complicated.
Layered structures may be done as well, just by manipulating the voltage, in the most simple case maybe even from the soundcard of a PC via an
amplifier.
|
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
