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Post by Deleted on Mar 21, 2010 19:11:14 GMT
I bought an antique tulwar from forum member Trajan several weeks ago. There was rust on the blade under the langets where it was hard to get at (Trajan had cleaned the rest of the blade), and the iron hilt, formerly covered in silver foil, was VERY rusty. I had thought about blasting it, but that can erode good metal along with the rust. I did a little research, and discovered electrolytic rust removal. I believe this is a technique that museums also use to conserve dug artifacts. Basically, you take a 12-volt DC power source (I used a modified ATX computer power supply; a battery charger will work, but you need the kind that does not "power down" once a battery is fully charged). Fill a plastic tub with a solution of washing soda, which is sodium carbonate. If you can't find washing soda, either cook some baking soda at 300 degrees or more, or do like I did and use a little "OxyClean", which is sodium carbonate and sodium percarbonate. Hook your positive lead to a piece of scrap iron, preferably the same general surface area as the piece to be de-rusted. Hook the negative lead to the rusty piece. If you can surround the rusty piece with pieces of scrap iron, all electrically connected, that's even better, since the process pretty much works "line-of-sight" between the rusty piece and the scrap iron (which is a sacrificial anode). Otherwise, just turn the piece every so often to present a fresh surface to the anode. If the solution starts getting a little low, due to evaporation or the electrolytic breakdown of the water, just add more water. After a couple days of treatment, take the piece out and scrub the loose black "sludge" off the piece with a brass bristle brush under hot water. You will be left with clean, grey iron or steel. It will not harm non ferrous metals like brass or silver (though if there is any rust under any plating, the plating will come off in those areas along with the rust, due to physical rather than electro-chemical reaction). Oil the clean metal right away, as it will quickly begin to re-form a thin layer of rust (which should easily come off with steel wool and oil). This process even removes rust from inside pits and detailed areas. Steel or iron that was already shiny and rust-free will remain that way. before: after: before: after: [glow=red,2,300] WARNINGS:[/glow] NEVER use stainless steel for your sacrificial anode, as this will release hexavalent chromium into the solution. Hexavalent chromium is a group 1 carcinogen (watch the movie "Erin Brockovitch", if you want some idea). Also, do this in a well ventilated area away from sparks, open flames, or other ignition sources, as the process generates HYDROGEN and OXYGEN in the nasty rust-colored foam that will form on top of the electrolyte solution. The waste solution, by the way, is environmentally harmless (unless you used stainless steel for the anode...), and can be simply dumped on your lawn (although some ornamental shrubs that don't like high iron concentrations may be harmed).
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Post by Deleted on Mar 23, 2010 15:29:22 GMT
Awesome post!
I had read about this in the past and had always wanted to see some before and after pictures, and now I have! I'm also glad that you put in the warnings at the end there. I had remembered something harmful about stainless steel, but couldn't remember what. If you hadn't put it there, I was going to look it up and add a warning.
Great stuff all around. +1 from me
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Marc Ridgeway
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Post by Marc Ridgeway on Mar 23, 2010 15:53:57 GMT
Indeed a good post... in fact... a STICkYED post. Nice information.
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Post by Deleted on Mar 25, 2010 1:07:23 GMT
I probably don't have to say this, but just in case... It is important to have a good electrical contact between your piece to be treated and your negative lead. If necessary, sand a small area to clear away the rust before attatching the lead. I got lucky - the blade is firmly in contact with the hilt, both with shellac and an iron rivet, so I was able to hook my negative lead directly to the blade. Happy cleaning!
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Post by muerteblack on Mar 25, 2010 20:11:11 GMT
Very nice looking method! However, what are your thoughts as to the assertion that this method will destroy the heat treatment of a blade as read here? www.trueswords.com/sword_care_maintenance.phpAlthough of course once rust has gotten THAT bad, it may be too late to save as a viable cutting weapon anyway, but I was still just wondering.
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Post by Dan Davis on Mar 25, 2010 21:41:09 GMT
This is a distinct possibility; as birdman originally pointed out this is a conservation technique that is only suitable for reclamation of antique weapons.
Hardness in steel is a function of not only the presence of carbon but the molecular structure of the iron. Reverse electrolysis converts iron oxides back into iron but it is deposited as elemental iron, having the most basic free iron form. Any martensitic iron molecules affected by the process will be broken down into pearlite, removing hardness from the steel.
For this reason I would NOT recommend using this process on any blade you intend to use.
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Post by Deleted on Mar 27, 2010 11:54:06 GMT
The electrolytic process does not seem to generate any significant amounts of heat - certainly not enough to destroy the temper. None of the research I did on the process before attempting it mentioned anything about damaging metal, only rust. It is a surface-affecting process, which is why only rust is affected and unrusted metal is untouched. I also noticed that the article from TrueSwords mentioned using zinc as an anode; the only mention of zinc I found said that galvanized metal wouldn't yield good results. Plain scrap iron was the recommended anode. Also, the TrueSwords article mentioned using lye or caustic soda as an electrolyte, but I read in my research at one point that trhis can harm metal once the current is turned off. Best to stick with sodium carbonate - it works, and isn't going to burn you.
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Post by Dan Davis on Mar 27, 2010 14:34:35 GMT
I did not say anything at all about heat, did I? It is not heat that affects the temper, it is the fact that the electro-chemical process which converts the iron oxide back to pure iron (getting rid of the oxygen) also changes the molecular structure of the iron.
It is not strictly a surface-only affect either; it affects any place where the electrolyte can reach, including the interstices where the grain of the steel is open. while it only affects rust molecules (iron oxides), those molecules can exist very deep inside a blade, particularly if the grain is open.
I agree that caustic soda or lye is a bit of overkill on a sword blade, but when you are restoring bigger things (iron cannon from an English galleon, for example) you need a much stronger electrolyte. Those solutions will also harm steel if it is left soaking in them, so I agree that they should probably not be used for swords.
As for zinc, this is a common sacrificial anode used in these processes; it works fine. The reason galvanized steel does not work well is that the galvanic coating on the metal forms an oxide bond that is very hard to break down (the whole purpose behind galvanizing). Pure zinc does not have this difficulty and since it is only serving as an ion exchange source it will not affect the metal you are reclaiming.
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Post by Deleted on Mar 27, 2010 21:29:08 GMT
Interesting. My understanding of tempering and heat-treating of carbon steel always had to do with how the carbon and iron molecules - iron carbides - were "layered" and packed together in the grain structure, and that tempering was all to do with heating the blade to "loosen" the structure, quenching to "tighten" the structure, and then reheating to a certain degree to SLIGHTLY "loosen" the structure and remove brittleness. At least, that's how my farrier/blacksmith uncle explained it to me years ago. It's also why true wootz "damascus" can't be worked at more than a red heat, as more than that will destroy the grain structure and you end up with simply very high-carbon steel that is too brittle to be good cutlery - it's all about the distribution of the iron carbides. Could you please show me a source that tells how the electrolytic process affects the complete molecular structure of the steel and destroys heat treatment, because I have thus far been unable to find anything online.
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Post by Deleted on Mar 27, 2010 21:58:50 GMT
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Post by Dan Davis on Mar 27, 2010 23:28:00 GMT
Interesting. My understanding of tempering and heat-treating of carbon steel always had to do with how the carbon and iron molecules - iron carbides - were "layered" and packed together in the grain structure, and that tempering was all to do with heating the blade to "loosen" the structure, quenching to "tighten" the structure, and then reheating to a certain degree to SLIGHTLY "loosen" the structure and remove brittleness. At least, that's how my farrier/blacksmith uncle explained it to me years ago. It's also why true wootz "damascus" can't be worked at more than a red heat, as more than that will destroy the grain structure and you end up with simply very high-carbon steel that is too brittle to be good cutlery - it's all about the distribution of the iron carbides. Could you please show me a source that tells how the electrolytic process affects the complete molecular structure of the steel and destroys heat treatment, because I have thus far been unable to find anything online. Sounds to me like your uncle had a very good grasp on what is going on in the steel, he sounds like my kind of guy. While the "wootz" method of forming ferric carbide is a very viable way to harden metal but it is NOT the most common; in fact it is so UNCOMMON that it was considered "magic" throughout most of history. For the most part, steel is hardened by the formation of martensite, NOT ferric carbide. The COMMON method of hardening is to heat the steel as a monolithic piece to a temperature above which allotropic phase transformation occurs in the steel molecules. At this point the molecular structure of iron shifts from a body-centered cubic structure composed of 9 iron atoms to a face-centered cubic structure composed of 14 iron atoms. Also at this point, the cubic structure is hollow and greatly expanded due to the heat, so carbon atoms can enter the cube and rest at the center. By rapidly quenching the steel you cause the lattice of the iron molecule to shrink fast enough that the carbon atoms in the center cannot escape. The molecule will shed the additional 6 iron atoms located on the faces but cannot replace the carbon atom (big) with an iron atom (small) and so the crystalline structure becomes distorted and creates hardness. This occurs because the regular but distorted crystalline shape prevents the iron molecules from forming the long molecular chains or "strings". As you can imagine, most of the carbon atoms will be trapped neatly inside the crystal but some will be mostly in, some will be mostly out, and others will be at every stage in between. These greatly distorted crystals cause stress points in the overall structure of the steel, which makes fracture far more likely. By raising the steel to a temperature somewhat greater than ambient, but below the point where phase transformation starts to occur again, you can expand and thereby "relax" the tightly closed crystalline structures, allowing the carbon atoms to migrate into or out of the cubic iron molecule. This in turn gets rid of the highly distorted crystals and makes the steel far more resilient. To answer your question re. electrolysis, when iron oxides are formed on the perimeter of crystalline iron molecules the oxygen attaches itself to the outside of the cubic structure, causing crystalline growth and weakening the ionic bonds between the iron atoms themselves. The electrolytic process actually breaks all the ionic bonds, strips away the oxygen and leaves elemental iron (single iron atoms) behind. Hardness relies upon the distorted crystalline structure of the martensitic molecular form so anything which breaks down that structure effectively removes martensite from the blade and reduces hardness.
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Post by Deleted on Mar 28, 2010 1:32:27 GMT
Hmmm...how much damage would likely have been done to my sword blade in 48 hours or so? It is very thick at that point (I only immersed it to the end of the hilt langets) - about 5/16" thick or so, actually. It's quite the heavy blade. Thankfully, it's not at a place where the edge would be doing much actual cutting. I'd hate to think I ruined a good fighting blade...
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Post by Dan Davis on Mar 28, 2010 12:29:43 GMT
Well, I am of the personal opinion that if there is enough rust to actually damage the usability of a blade then you know it before you start.
Your solution was relatively mild and we can see where the very hard black rust remains in the crevices of the blade. It seems likely that you only affected the surface rust, where most of the damage has already been done.
From what I can see of the blade it does not look like you did any harm to it, but unless I absolutely had to I would not use that blade in any case, it has more value as an antique.
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Post by Deleted on Mar 28, 2010 13:32:27 GMT
Not that I plan to use it for anything other than light cutting. It's just that I don't like totally useless (read: non-functional) weapons and armor, or ones I'd be afraid to use or handle for fear of ruining value. I DO use some of my antique weapons, especially guns (I have an original P1853 Enfield rifle-musket and a Smith & Wesson #2 revolver that I shoot, the latter with special reloadable rimfire cartridges that use .22 blanks for primers), but when I buy such things I buy "user's grade" rather than "investment grade", and treat them carefully.
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Post by Dan Davis on Mar 28, 2010 14:47:05 GMT
Well, it should be fine for light cutting. I see no reason not to use a weapon for what it is intended, even if it is an antique, as long as it is still suitable for it's purpose. I prefer to buy modern pieces though and save the historical pieces for study, but then again I am a bladesmith.
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Post by Deleted on Sept 19, 2010 22:40:29 GMT
Bye the way this method also works on old firearms inside the barrel. Not sure the exact process but look up removes copper fouling and such.
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