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Cleaning the Blade

Cleaning the Blade

I start off by using a razor blade and some mineral spirits to scrape as much of the rust off of the blade that I can:

 

When it's as clean as I can get it with the scraper, it's time for an electrolysis bath.  The container I picked up at Walmart for about $5 - after I'm done using it here, I clean it out with a hose and a rag, and it comes perfectly clean for use elsewhere.  The water in the bath is a mix of about 1 tablespoon per gallon of washing soda.  The black (negative) clamp of the battery charger is hooked directly to the blade, and the red (positive) is hooked to an old cookie tin used as a sacrificial anode.  Don't use something here that you want to save - you'll see why a bit later.  The negative clamp can be in the water, but the positive must be kept out of the water or it will rust away, and quickly.

Here you can see the bubbles starting to form on the saw blade, showing it's working.  I left this in the solution for a couple hours, took it out and scraped it again, then left it in overnight to get as much of the rust as I could.

One additional note when you use electrolysis - it turns the rust into a black powder that can be a pain to remove.  Since this is a user, and not a collector's saw, I don't worry about it - I'm only worried about killing the rust.  You might want to take it into consideration.

Added 1/09/05:  A possibly better solution than electrolysis has been suggested to me.  I've been talking with a fellow who's been using citric acid and achieving excellent results.  I'm intrigued enough to try it on my own one of these days...  I'll post my results here when I do.  Citric acid is available at outlets selling swimming pool chemicals - it's used to balance the pH level of the water.  A good discussion of it is posted in the oldtools archive, if you want to read a bit more on it:
OldTools Discussion #1
OldTools Discussion #2
OldTools Discussion #3
I hope to have something more on this to add here in the next few months sometime.
 
 On Citric Acid and Electrolysis:
Added 06/07/05: 
I was asked the following question on using electrolysis and citric acid:
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Hello!

You refer to this citric acid method to remove rust. However at a homepage I have read that acid weakens the metal. The following is written there: "All acids contribute some hydrogen to the metal structure. This weakens steel by a process called hydrogen embrittlement. If the metal is a cutting tool or gun barrel, for example, this weakening can be dangerous. One person claimed that if you bake the metal at 400F for an hour after acid cleaning, then you can drive out the hydrogen and prevent this embrittlement."

What do you think about it.

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My answer:
Yes, acid will weaken the metal - but I don't think it's a big issue if you only leave the metal in the acid solution for no more than a few hours. After all - rust weakens the metal too! Any process that removes metal, be it cooking it with electrolysis, bathing it in chemicals, or letting it rust in the weather - will weaken the metal. I think too much is made of "hydrogen embrittlement" as far as hand saws are concerned, as it really only applies to larger scale or longer term work than what we are concerned with and doesn't really relate much to hobbyists such as we are. Just be sure to wash off the blade well when you are finished with the acid - it might be a good idea to use a mix of water and baking soda to neutralize the acid when you are finished.

"Hydrogen embrittlement" has also been brought up as an issue when using electrolysis. I've done more than a few saws using electrolysis, and use those saws regularly - and not one of them is "brittle" in my opinion. But, of course - any process taken to an extreme is probably doing more damage than good, so use common sense, and don't overdo any of it.

I don't think I would bake the metal at 400 degrees, as that could mess with the temper of the blade, and result in softening the steel. Then it might not hold an edge well. The metal used in saws is quite similar to O1 tool steel - which after hardening, you temper by placing in a 350-400 degree oven for an hour - sounds close to the above, no? That's what would concern me - you are essentially tempering the steel, softening it. For more reading on heat-treating tool steel, there's a nice little web page here:

http://www.threeplanes.net/toolsteel.html

Now - having said all that, both citric acid and electrolysis can leave behind a finish that is not all that pretty - a black or dead grey look. If you want to avoid that and everything mentioned above - instead of zapping or chemically bathing the saw, you can simply sand it using wet/dry sandpaper and a medium such as mineral spirits or turpentine. The medium is not all that important, you could probably use water - it's only there to carry away the swarf/rust and keep it from clogging the sandpaper prematurely.

That avoids all of the above problems, including "hydrogen embrittlement" Start by scraping the big flakes off with a razor blade scraper, then move on to no coarser than say 120 grit sandpaper or so (the finer you can get away with, the better!), then upwards in grit until you are satisfied with the finish. If the rust isn't bad, you can also do the same process using different grades of steel wool, instead. If you want, you can even go beyond that, and polish the metal to a high shine using pumice, rottenstone, automotive buffing compounds, or whatever - until you have the shine of the blade just where you want it.

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