Very very small parts and copper/nickel

[xiphmont]

Hello! Not a plea for help this time

I've noticed that the plating manual doesn't really cover plating tiny, tiny things (~.5sq in) and I'd been having *alot* of trouble with it.

After trying everything in order, I found what worked. for this tiny part, I'm plating copper at nearly 2A per square inch! Why? Because at less than about .5-.7v, no copper moves at all. With this part in the bath at the recommended 25-50ma, the voltmeter reads about .2v. After a whole night of utterly failed 1 hour runs (which did nothing but turn the part in question a dark grey), I kept upping amperage until I hit one volt, the recommended minimum voltage.

Bingo. A *perfect* copper plate. Better, even, than I dreamed was possible. And in only ten minutes. Really stunning, mirror smooth copper. Wow. Wow. The ampmeter, at this point, read 1.2A.

Do any of the real gurus have a better very-small-parts voltage-amperage table to offer?

Monty

[xiphmont]

Since pocket change is plentiful, and nickels and pennies approximate the base metal and final nickel-plate-on-copper, I've been making copper nickels and nickel-pennies for two days at various current levels. I'll plot up a graph here once I finish.

Copper just doesn't plate at all reliably under ~ .4v. At .2-.4v, it will plate, but does not cover evenly. At .2v, the plate will never amount to more than a patchy haze... where it sticks at all (it will rub off very easily as well).

When copper-plating a nickel (almost exactly one square inch), even at .3v, the current was already at two-and-a-half times recommended setting, but the copper just wouldn't move through the electrolyte. Coverage at 3v left about half the nickel uncovered (not following low/high areas, just random total lack of copper coverage)

The best plate I saw was around .8v. At 1v, the minimum recommended plating voltage in the manual, the current was so high (a full amp for only one square inch!) that the sharp edges already looked like they were just beginning to 'burn'. At 1.5v (and 1.5 A), the plate looked very 'burned' around the edges. Below .8v (700mA), the plate appeared progressively duller and less even, although it still looked quite good down to about half a volt.

The copy chrome solution showed a different behavior; even at 5mA, the plate voltage never dropped as low as the recommended minimum voltage of 1.5v. The standard instructions seem to work just fine here for tiny parts.

Summary:

V=IR just doesn't hold. The electrolyte is not a linear resistor. So it looks like the pure linear 'amperage per square inch' rule doesn't hold at the far low-end of the plating spectrum, at very least for copper (where silmultaneously acheiving recommended voltage and amperage were impossible). Nickel still plated fine following directions exactly, but might benefit from fine tuning; when plating pennies, plate quality dropped rapidly under the recommended voltage/amperage combination; however, I had to exceed recommended amperage by almost a factor of ten to see dark too-much-amperage-streaks in the copy chromed pennies.

Monty

[mcaswell]

As you state in your post, the recommended minimum voltage for copper plating is 1V. When plating very small parts, you'll need at least 1V (regardless of amps) to start the plating process.

It seems as if your findings support this.

We'll likely incorporate some of your posting into future versions of the manual, so keep it up.