lahthffire
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Nickel on Aluminum - electroplating
I'm trying to plate nickel onto aluminum via brush plating (where you brush an anode soaked in plating solution (graphite wrapped in cotton) onto your
cathodic workpiece). I talked to a brush plating place that said you could either go through all of the various electrochemical cleaning/desmutting
procedures to remove the Al2O3 layer, or you could simply blast it with 100 grit alumina, then plate right away.
Well I thought about that and figured that if simply bead blasting was sufficient to prepare the surface for plating, then maybe plating immediately
after machining the surface would work. So I gave it a try.
The Ni, however, would not stick to the freshly cut Al surface worth a damn. It would kind of go on, but it looked like crap, and immediately started
peeling off.
So I blasted a couple of pieces with alumina and tried plating those and they plated fine. The finish is not shiny, however, because the blasting
roughs up the surface. And it has a slight gold tint.
I looked at both surfaces under a microscope and on the freshly machined/plated aluminum, it was clear that there was no adhesion between the Ni and
the Al. The Ni formed tiny little balls which simply sat ontop of the Al and conglomerated, sticking to themselves.
Upon close inspection of the blasted pieces, it looks like the same behavior may be happening to some extent. However, the adhesion is way greater.
Can someone explain what may be the reason for the difference between the two surface preparation methods? The blasting does rough the surface up, but
not on any kind of micro level. Under the microscope I can see each and every depression made by the grains of blasting medium. The Ni plating follows
the peaks and valleys. It seems like if blasting is removing the oxide layer and it doesn't form rapidly and thickly enough to hinder immediate
plating, then freshly machining the surface should behave the same way.
Is it possible that stress has anything to do with it? The machined surface would be subject to tensile stresses, while the blasted surface would be
subjected to compressive stresses.
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12AX7
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Erm... lube?
Wait, don't tell me you machine dry! Gack!
Tim
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lahthffire
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Yes, I machined it dry, just so I wouldn't have to worry about whether or not I cleaned it thoroughly enough afterwards. No big deal on aluminum.
I usually do use some type of cutting fluid, though, unless I'm machining brass.
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