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Posted: 5/31/2012 6:12:55 PM EDT
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Some people have followed my learning curve on rust bluing in my Mauser thread, today I learned something new. From my many mistakes, I have learned that you can polish back rust blue to fix bad spots, and re-rust it back up to a good match with the rest of the finish.
So what, I wondered, would happen if you wanted to make a "blue repair"? That is, patch in the bluing on something that was worn out and patchy, without going to the trouble to completly strip and polish it? Lying on my bench was the 1920's magazine to an old Savage 25-20 Bolt gun that is one of my project/toys. It hasn't been out of the box in a while, and the magazine has been wandering around the bench. It is old, and rusty, wearing it's original 90 year old finish( or what's left of it). Experiment time 
I didn't do any prep, other than steel wool it, (dry), scrub it in denatured alcohol with a toothbrush, and boil it in distilled water. No sanding or polishing, no removing old blue. First rust 
After two rusts,no oil or polish, I'll probably try another rust to see if I can get more out of it. 
Pretty impressive, it's already a nice black, and looks 100 times better than it did. I'm sure with a coat of oil it will look great. It still has all the dings, and scratches, and some rusty spots I wish I'd taken more time to sand off, but I learned that you CAN patch blue and get a decent finish back on, at least small parts like this. Now the whole rifle is on the list.... Rust blue is an excellent way to stovetop blue small parts, and a great way for the home gunsmith to get a decent finish on a rifle. It's a Black oxide, not really all that blue, but it is easy and forgiving and makes a nice finish for a rifle. I'm very happy with my results and wish I'd figured this out twenty years ago.. |
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I've tried a recipe I've found on the 'net some days ago. It involves boiling the part in distilled water white vinegar. Basically, the vinegar starts the rustin process, the boiling water transforms red rust into black oxide. it works, it's fast, it's a deep black. |
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Quoted:
I've tried a recipe I've found on the 'net some days ago. It involves boiling the part in distilled water white vinegar. Basically, the vinegar starts the rustin process, the boiling water transforms red rust into black oxide. it works, it's fast, it's a deep black. Hmmm, I'll have to try vinegar. My bottle of Brownells is at end, and I have a barrel to blue. Brownells has been out of stock for months now, they finally got Pilkingtons back in, but I'm too cheap to pay $32 for 4 ounces.. I was considering, and researching mixing my own solution with muratic, or rusting by fume in a cabinet. I think it doesn't matter what agent you use to start the rust, as long as it is not aggressive enough to eat the metal and you can get a slow, controlled rust. I read of one gunsmith who used no agent at all, merely a steam cabinet to cause rust. The key is bare, clean metal that will rust uniformally. |
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I can't seem to find my copy of Firearms Bluing and Browning, but it contains hundreds of formulas used for rust bluing, including some that are supposed to be good on stainless steel. (Not too sure how they would work on modern day stainless steel, the book was published in the 1930s).
A simple one I do remember was ammonium chloride. He even tried a simple salt solution, and it worked after a fashion. Most of the formulas included nitric acid. Kind of difficult to obtain a small quantity of nitric acid these days, though. Hydrochloric acid is easy, though. My experience has all been with Pilkington's, and it does work well. I will try some thing else next time, though. |
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Brownells has been out of Their cheap Classic Rust Blue for months, which is what I use. So I'm in the mood to experiment and come up with a solution that works.
The limited number of solutions I've found involved Nitric acid, Sulfuric acid, dissolving iron in it, then diluteing. I'm going to play around with muratic, diluted sulfuric acid, which I have on hand and have used extensively cleaning metal parts, and try disolving iron in it and diluting it to different strengths and trying it out on scrap steel. The diluting in the final steps of the Nitric /Sulfuric acid seems to my simple mind as a long way around to arrive at a solution of lightly diluted Muratic.Muratic certainly rusts clean steel well enough, the trick seems to be slowing it down enough to prevent it from etching the finish of the metal. I'm also considering a fuming cabinet, vineger, and maybe even buying the book!
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