Electrolysis

Where in the world is Nick, he uses a hotmail address and the German news server so could be anywhere. His messages are timed to be somewhere around the far end of the med, maybe a bit further east:

Date: Fri, 17 Sep 2004 20:08:29 +0300

Mind you Peter you seem to have dropped summer time before the rest of us. B-)

Date: Sat, 18 Sep 2004 07:14:04 +0000 (UTC)

"Dave Liquorice" wrote (sniP):-

Je habite au West London innit!

Hot mail addy was initially set up as a throwaway on the assumption that subscribing to this NG would attract a whole heap of spam, hasn't really happened though and the spam filtering is pretty good anyway so I now tend to use for most things. I use German news server as it was recommended to me when mailgate went t**s up. Sorry about the clock, but it's pretty low on my list of things to sort.

If there is a plot to be lost it is always safest initially to assume that oneself has lost it!

Right, best stop hijacking this thread!

I have only practised the dark art of electrolysis on a small (ice cream tub) scale basically to prove to myself that it works, and it certainly does. I used a small battery charger and stainless electrodes, having read at the time that that was the thing, but I shall heed the warnings and use mild steel next time.

One can throw a thin coating of copper onto iron or steel simply by immersing in a solution of copper sulphate - no 'lectrickery required

Nick, Dont apologise I was just curious because initially I thought it was me who had lost the plot when I saw your time :-))

Martin P

My problem is I can never find a good plot to loose :-))

Martin P

Kettle,pot and black I think oop's done it again :-))

Isn't electroplating the reverse of electrolosis and how easy is that, dont you need salts in the water relevant to the metal.

I know as a kid at school we used to coat steel in copper would that not work well as an anti rust agent!

Martin P

Copper coating is used on some MIG welding wires, partly to inhibit rusting, but it only has a very limited effect. I can show you the rusty reels of wire to prove it! I suppose it's fairly porous until you get do a decent thickness?

Cheers Tim

>

Sorry Tim, What I meant to add was " prior to painting"

Martin P

Hi Peter, I posted a question about this some time ago with a URL of a site that gave some good information. Unfortunately I can't find it now. However, Try this site.

could also try asking the rec.crafts.metalworking NG. They are sure to be able to help.

John

Which is very handy to know if you ever need to solder a wire onto a steel spring. One drop of copper sulphate solution, wait 5 minutes, wash off and dry thoroughly and it will take solder a treat if you solder it immediately.

The principle behind electrolytic rust removal is quite simple. monatomic Hydrogen is liberated at the cathode which is extremely active until it combines into normal H2 hydogen gas and before it 'pairs up' some of it reduces the iron oxide (rust) to a lower oxidation level or even back to metallic iron which causes it to shrink and drop off the iron or steel surface. Meanwhile the Anode is geting assaulted by extremely active hydroxyl radicles so corrodes in a jiffy. Ideally the anode would need to be made of a material resistant to extremely oxidising solutions. Any metal that would be attacked by nitric acid will probably dissolve if used as an electrolysis anode. Aluminum and Titanium are definately unsuitable as they will form a heavy oxide layer which will block most of the current. Gold or platinum would work just fine but who could afford a platinum bucket? It would be interesting to try a graphite electrode but I dont have access to any large slabs of the stuff. Meanwhile I use whatever scrap steel sheet I have handy in a form that its easy to clean up a bit with an angle grinder when the current drops too low. I use a car headlamp bulb in the +ve lead to the tank as a 'ballast' and to prevent the power supply complaining if any part touches the anode.

So fa I've only done tools and a few small parts off my Seagull. Now if any of you could tell me an easy way of zinc plating small parts, I would be interested.

It worked well enough for me using a small domestic battery charger. Boiled away merrily but was pretty line of sight as you'd expect. As I was trying to de-clag an ST P55 block, it had limited success.

The crud in the bottom looked pretty vile and it would have never occurred to me to spread it on the lawn as it makes good fertiliser!

I must have missed the bit about stainless steel. Why should one not use it?

Something I've seen no-one mention is that this process will dissolve zinc and aluminium. I tried it with ali and a sand cast ALCO Featherweight valve cover showed etching damage within ten minutes. Any other metals react badly?

Regards,

Kim Siddorn

Yes. More because of shadowing than any "short circuit" effect. It's ferrous gunk down there, but it's too particulate to be a good conductor.

My de-rusting tank just has a layer of plastic mesh (old folding crate) spaced an inch above the base.

No. _Anodic_cleaning_ (aka electropolishing) is the reverse of electroplating. This is a powerful cleaning process, but it's destructive. I do sometimes use it in manufacturing, but not for restoration.

Electrolytic de-rusting is more like electroplating (same polarity) but without the dissolved metal. In the absence of metal, the plating action is instead to strip oxygen from the surface of the metal, converting ferrous oxides back to iron. Obviously this process is self-limiting, once all the iron oxide has been reduced. This is a great advantage in making the process workable !

Read the sorry story in rec.woodworking of someone who got the connections the wrong way round and reduced a compass plane to powdered scrap....

The typical misunderstanding with electroplating is that you're taking metal from the anode to the cathode. You're not - you're plating on metals that were _already_ dissolved in the electrolyte solution.

For _some_ processes, you use a matching anode and you replenish the electrolyte while you work (copper, nickel). For other processes (chrome) you use a lead peroxide coated lead electrode (very like a car battery plate) and this doesn't dissolve. You replenish the chrome by adding it as metal salts to top up the electrolyte. Either way, this is only an issue for long-term industrial processes. For the likes of us, we kick off a bucketful of brew and we run it just the once.

There are also "electroless" processes, typically used for putting down nickel on steel. These use the internal electronegativity of dissimilar metals to plate from solution just by immersion, without needing any applied voltage. They have some advantages - they're somewhat easier, they don't have "shadowing" effects and they give an even coating on any shape, even spiky needles with deep holes drilled inside. Electroless nickel is thus particularly good for non-conductors and electroforming.

Caswells will sell you an electroless nickel plating kit for about £55 quid (Kim, I might have one of these soon, if you're interested)

As a general principle, "steel can't be copper plated".

You can do this with a cyanide process, which we're not going to mess with at the "home workshop" level. You can't do it with the acid copper process, because that attacks the underlying steel. In fact you can do it, because an acid copper bath works as an electroless bath on steel - but the results are poor and the deposit isn't so much porous as has thumping great holes burnt in it ! It's an attractive patina effect and you might use it decoratively, but it won;t work for rustproofing.

If you really want to copper plate steel, the trick is to electroless nickel it first, then acid copper onto that. Acid copper is a well behaved process and the only base metal plating process that really works at home (I've an ongoing project to do a pair of leather boots). Copper is also a cheap process - about ten quid gets you a bucketful of copper sulphate solution big enough to do engine components. Crystalline CuSO4 comes from a farm shop, as a sheep fungicide, and a little conc. sulphuric drain cleaner to control the pH.

So how do they put the copper coating onto MIG wire? is it rolled on, mechanically, perhaps?

Cheers Tim

the copper coating, here in the us, is electrolyticly (sp?) deposited when the bar is about 3/8 inch diameter and it is drawn with the bar down to the final size. the machines i worked on went down to 1/16" final diameter. sammmm

Same as most copper plating - electroplated from a cyanide solution. This is a simple enough process, but it's not something you can safely work with at home.

In general, cyanide processes are preferred to acid processes because their electrochemistry is more efficient. This assumes an industrial scale process which is geared up to handle them - obviously the rules are differerent for kitchen sink work.