Hey, gang, here's a little something I whipped up over in sci.chem after asking if my article about prion chemistry was any good:
I have electrocleaned the battery clips on my grandfather's old Sears 6/12 volt battery charger with success. They don't come out shiny. See below.
This was an old copper-oxide semiconductor laminated rectifier and was marvellously resitant to abuse for that reason. It had a nice meter.
I threw it away when my first lover died and I did some house cleaning. I'd been holding onto the memory of my grandfather since he died in 1976, while I was away at high school in Germany. I didn't get to attend his funeral. Linda died in 2000. I held onto that piece of crap for 14 years. I still have his ruler, a nice steel engraved 6 inch ruler. Real quality, that. Will last forever.
Yup.
Duh!
Sorry, I think what you meant was chemical and electrical means only. That's the whole point, right?
Well, George, you're in for a bit of a fight, and here's why.
When you electroclean steel, the work is negative. When you electropolish it, the work is positive, and much more power is required.
When the work is negative, electrons available at the surface attract hydrogen (H), which is slightly postively charged by it's "bent" configuration in the water molecules. When hydrogen is an ion, it is H+. It cannot get any more positively charged than that, because it consists only of a proton nucleus, no neutrons, and a single electron orbiting the proton, or according to quantum mechanics, likely to be found near the proton according to a certain probablity density function which is surprisingly, quite easy to find.
So these hydrogen atoms leave their existing oxygen partners, and it is those oxygen atoms you see bubbling to the surface. Oxygen is negatively charged, usually. When the H combines with the O in Fe2O3, it forms H2O and "recycles" into solution, where it can be stripped again, forming another bubble nucleus of oxygen. And on and on. So the H shuttles back and forth, while the O in the rust goes to bound O in H2O, then is released as O2 when the H is pulled, yet again, to the negative electrode. Ambient heat "stirs" the water near the electrode.
Now, this leaves fine particles of iron, in fact one or two iron atoms at a time, "more or less" attached to the workpiece, but again, ambient heat can stir them into "solution", where they form a toxic powdered iron hazardous waste. On drying and mixing with an oxidizer like salt peter, this sludge may be ignited yielding the bright orange spark characteristic of a steel mill pouring hot iron into molds for milling. This can be dangerous. Do not mix metal powders with the hypochlorites, chlorites, chlorates, or perchlorates. It's quite dangerous.
So ambient heat rips the "cleaned" steel atoms from the work. The best you can expect at room temperature is to remove all the rust, create sludge, and end up with the steel, wherever it is sound, bared for your inspection.
Now when you look at it, it looks pretty ratty, but with electropolishing comes some hope of redemption. You have to understand surface roughness some. At least it helps. At this point the work is chemically clean, cleaner than anything else in the room, and will rust immediately.
Now, when you electropolish, the work is positive, just like for anodizing aluminum, which forms a protective coat of aluminum oxide on the metal, thicker and smoother than that formed by exposure to air. Only when you electropolish, you are ripping metal atoms from the surface, a mechanical process that takes large amounts of energy. The metal atoms like to go positive, for example Fe+ or Fe++, and to combine with them you have to get the oxygen atoms to separate from the water and combine with the iron, forming finely powdered rust, which can be recycled in a thermite reaction if mixed with the right oxidizer. Hydrogen bubbles to the surface. Rust falls to the bottom.
I am not going to disclose in this article the chemistry of a thermite reaction, because one can easily melt through a steel laboratory desk top, set a house on fire (they were used as incendiary weapons in WWI, destroy an engine block, or weld steel rail, which is what they are used for, mostly. I do not want anyone to get hurt just from reading what I write.
Anyway, for a reason I do not understand, this tends to happen on "asperities", which are the pointiest bits exposed by the electrocleaning. Electropolishing rounds off asperities by turning them to rust.
Now, to walk to the bottom of a valley is easy. You just head off downhill, stroll along easily, and in a few minutes or hours, you are there. But if you are an oxygen atom looking an iron atom, you are effectively coming vertically downward at a mountainous landscape and your job is to level the entire landscape one pebble at a time, until it's all valley.
Now what if you were a spoonful of dirt, and your job was to fill the valley? While not as easy as walking downhill, this is also not as hard as rounding off the mountains. So what we need to do is PLATE iron back onto the steel in a way that fills the valleys first, and we can worry about the little mountain tops later.
Well, to PLATE a metal, it must be an ION in SOLUTION, and we haven't got any. The removed rust fell as iron to the bottom of the tank, and the removed iron fell as rust. Neither is an ion. So if the solution is neutral in pH, that is, tap water with salt added, not acid or base, the above will happen and we won't be able to fill in the valleys, and rounding off the mountains will take a lifetime and the entire output of the Northestern grid, which went down recently, by the way.
So which way do we tweak the pH? Acid or base?
Surprisingly, I think either would do. All I know is that metal likes to be positive, so you either add an acid and hope it reacts with and dissolves the fine iron particles that fall off during electrocleaning, or you add a base, hoping that some of the iron atoms ripped from the solution will mate with the HO- instead of the O+, go into solution as what is called a "solution inventory" meaning there are essential no molecules of iron hydroxide left, they are all broken up.
Anyway, if you leave the solution neutral and then try to alternate stripping the rust and depositing fresh iron to plate over the valleys, what you end up with is iron over rust, not clean metal, which is why shit made in China is cheap, because they pour all their sludge into the river they drink from, and why it doesn't last, because it's iron plated rust. Now if you machine freshly cast or milled metal and dip it in Cosmoline, you can keep the surface clean essentially forever, and some of the good stuff I have got from China like my drill press follows this regimen closely.
So very little care (some oil or grease) is needed to PROTECT iron, but great effort and energy is required to REPAIR it, which is all the folks in the rec.crafts.metalworking newsgroup I love so much like to refinish old machine tools: it's fascinating.
At the very least, you will need a specification of electrolyte and sludge disposal regimen for two separate processes, the first of which must be taken to completion, that is, chemically clean metal, and the second of which can be taken as far as you like, be it filling up the valleys with plated iron, or another plating, or polishing down the mountains with the appropriate electrolyte and sludge disposal regimen for electropolishing. You really can't do both in the same can.
One of the problems with filling up the valleys is that the little dirt clods (iron ions in solution) are first attracted to the mountains. There is no such thing as electrical gravity. They don't just fall toward the surface, they are pulled, and if the first thing they encounter is a mountain peak, an asperity, they stick to it, making the surface even rougher.
Moral of the story:
Try to keep the blood from your cut finger off the drill bit you stuck through it. It doesn't just rust the tool; it can dull the cutting edge. And after you are done with any unplated steel tool, wipe it clean of any moisture and skin acids, oil it lightly, and put it somewhere safe.
Yours,
Doug Goncz Replikon Research (via aol.com)
Nuclear weapons are just Pu's way of ensuring that plenty of Pu will be available for The Next Big Experiment, outlined in a post to sci.physics.research at Google Groups under "supercritical"