I’m always searching for ways to improve rust and corrosion resistance on my airguns, as I live in a pretty damp apartment in a basement. My tools rust, my airguns rust, it’s a never-ending battle. Cold bluing with commercial products don’t work too well, eventually rust do appear. But, I found a new-to-me way to improve rust-resistance, it’s called rust bluing. After some research I found two method of doing it : slow rust bluing, and quick rust bluing.
Slow rust bluing have been used on firearms from the late 1800s to early 1900s I think, and seems to be extremely resistant to wear and corrosion. Actually it’s said to be as, or even more resistant than modern hot salts bluing. Manufacturers don’t use it anymore mainly because it’s very time consuming, and time is money! The process is to make the part rust in a controlled way to slowly build consecutive layers of black iron oxide, which is inert and somewhat ’’seals’’ the steel surface. It will take days to do an entire gun. Gippeto (Thanks Al!) has posted his experiment and results on the Canadian forum, and one can find lots of infos on the net. I won’t go too deep into the details of the process here, as there are many good sources to find informations about it.
Quick rust bluing is very similar but takes much less time, I believe it’s feasible to blue an entire gun in one day. I’ve tried my hand at it with a few small parts, one entire cycle takes about 1/2 to 3/4 of an hour. It will give a very dark grey, almost black finish, and once oiled it looks very nice. It’s a pretty simple process, and it doesn’t use any harsh and toxic chemicals, only products you’ll probably already have at home, except maybe for distilled water but that’s not hard to find. Here’s the recipe for the rusting solution I’ve used :
8 parts hydrogen peroxide
1 part white vinegar
Saturate with (ideally) non-iodized salt at room temperature
1 drop of dishwashing soap (as a wetting agent)
The process : First prepare your parts by de-greasing them, then sand them to remove old rust and pits if there’s any. I suggest going up to 400 grit, but you can stop at 220. Also I tried the process on old cold blued and hot-salts blued parts without de-bluing them and it worked well, just need to de-grease them carefully. Starting there, don’t touch the parts with your bare hands, use rubber/latex gloves.
Though not absolutely necessary, you can lightly pre-heat the parts (with a hair dryer, heat gun or over a baseboard heater) to speed up the process. Apply the solution with a cotton ball, small artist paintbrush or de-greased paper towel ONLY WHERE YOU WANT A BLUED SURFACE. Plug barrels ends and mask the surfaces you don’t want to blue. When you apply the solution go easy, you don’t want the solution to run or drip, the metal surface only needs to be ’’wet’’ otherwise it can cause spotting. Also don’t over-do it, don’t re-apply the solution many times at the same place, it won’t be more effective, BE PATIENT!
Shortly after applying the solution you should see it starting to bubble, and an orange-ish color will appear, this is red iron oxide starting to form. Now you need to let the parts dry, again you can use a mild heat source to speed-up the process. After the parts dried, you want to convert the red oxide into black oxide, this is done by immersing the parts in boiling distilled water. In under a minute you should see the parts turn black, with some yellow-ish or orange-ish residues. Take the parts out of the water and let them dry thoroughly, you may again use mild heat to help.
Next step will be to ’’card’’ the parts, for this you will need to rub them HARD with 0000 steel wool. Don’t be alarmed if you don’t see any difference right away, 3 or 4 cycles are usually necessary to start to see a darker color. Also I found that the higher the carbon content in the steel, the quicker you’ll see it darkening. My parts are made from 1018 low-carbon steel, and it took about 12 cycles to get them to the shade I wanted. I’ve tested a piece of 1045 medium-carbon steel, and it took only 8 cycles to get it to the same shade as the 1018. Do as many cycles as you want, up to when you reach the color you want. Once you have the color you want after carding, generously apply your favorite oil on the parts, and yet again mildly heating them will help by opening the metal’s pores. Let sit for at least 12 hours, wipe down the excess oil left, and you’re done.
As with many things, practice leads to perfection!!! I suggest practicing on some scrap parts to give you a good idea of the whole process before attempting to blue your parts. Also this process only works on carbon steels, not on stainless steels, aluminum or brass. I’ve also noted that it doesn’t seem to change the parts dimensions, my dovetailed front sight fits exactly the same as before. And lastly, cleanliness is next to godliness, keep your bare hands off the parts as long as the entire bluing process is not finished.
Here are a few links that may be helpful, but of course feel free to explore further :
https://www.youtube.com/watch?v=7lXeT2qzCi0https://www.youtube.com/watch?v=xmv58Z3RZ9chttps://www.canadianairguns.com/showthr ... icals-quothttps://www.rustblue.com/blog/rust-bluing-woes/First pic shows the previously cold blued parts, second pic shows the newly rust blued parts:
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