This Corrosion

[e_spy]

Spent yesterday over at Making Space in Havant messing with electrochemical etching. I've done a moderate amount of marking of steel, but somehow have never got around to doing any deeper etches (which is daft really, given the kit I've got

Comments

[cursingchemist]

A very interesting test piece. I note that you simply used salt water as electrolyte. I found that this electrolyte became rapidly 'muddy' (ferric hydroxide, expected as the solution becomes progessively more alkaline in operation), and found that acidifying it (I first used white vinegar saturated with salt, and later salt water with a generous dash of hydrochloric acid) seemed better. I did not use mesh (or other 'bag') over the cathode, but I stuck it inside a piece of plastic pipe with a large number of small holes drilled in it, which kept the worst of the sludge and annoying bubbles confined, and avoided accidental shorts against the cathode when moving the work around

[e_spy]

Thanks for that - this was a fairly Heath-Robinson approach, which amused me given my inclination to over-think things

[cursingchemist]

>any likelihood of ferric chloride being formed

[e_spy]

I'm not sure I can believe NaOH being formed, that sounds like a lye to me

[cursingchemist]

>So what is inhibiting the reaction over time

[e_spy]

Oh, there definitely was some chlorine generated... Given the theoretical 7A output of the charger (and the lack of control - no load in series other than the cell) I think there's a good chance there was too much current draw.

Hmm, didn't know that was a known brightener - Googling tends to overload with proprietary compounds for electroforming. Fine if I'm doing anything commercial, but for just having a play I don't really see the need to go fully tech on it.

Oops. Mea culpa! The oldest I've used were the No4's; I'd fixated on the hammer mechanism and overlooked the breech. If the sight improves accuracy, then that is all that matters really! Although I have to admit to a fondness for more modern optics and overpriced image intensifiers.

[cursingchemist]

I'd reduce the current. Generating a load of chlorine and spray is simply going to corrode everything around the apparatus and generally increase noxiouness, and the excessive gassing is likely to help lift any ground that isn't stuck too well.

>I have to admit to a fondness for more modern optics and overpriced image intensifiers

Anyone remotely fond of anything optical doesnt put it near a black-powder gun!
These things belch out smoke, fouling and dirty lube!