Birchwood Casey Fast-Acting Long-Lasting Spanish Perma Blue Liquid Gun Blue for Steel, Touch-Up & Complete Reblue, 3 FL OZ (90ml)

Works great. Not just for guns, also works for other steel parts that are prone to rust.

Great product!

ItsIts in Spanish. But it still instantly forms black iron oxide on any iron or carbon steel surface. Degrease surface with alcohol and acetone first. Work quickly and neutralize with water within minute or so of applying it liberally with a swab or brush, dry and apply oil. Dont contaminate the bottle, pour or pipette out what you need, dont just smash a rag on it. Completely remove the seal on first use or it will contaminate the whole bottle. Wear gloves of course lol.

Works great!

Helps with toning down brass and silver

I used this on my Glock 19 for some surface scuffs that I caused by putting on new sights. I used a Vism rear sight tool and I did not adjust it quite right and it slightly drug the rear chuck across the slide. It caused a few minor scuffs or dings about a half inch long. I was going to use the Birchwood Casey flat black touch up marker like others have said worked, but after I got it I decided heck no. It would have looked terrible.So I thought what the hey, I would try it with the perma blue and try one small spot. IT WORKS. I end up doing the rest of the marks and now you cannot even tell they were there. It was just deep enough that I could see metal and it was driving me crazy. I even tried Hoppes no 9 first, just to make sure it wasn't surface transferI did some searching on the best way to do this. I heated up the slide with a heat gun to get it warm. Apparently it works better if the metal is warm. If you get it too hot, it will stink when the perma blue hits the hot metal, but still worked, I just kept applying until it got dark enough and then rinsed it with water to stop the reaction. When done, I wiped it down with gun oil and buffed it with the cloth.I also did my dad's Vietnam bayonet and it turned out awesome. I was trying to sharpen it years ago and it just left a lot of scuffing. I heated the knife, added the perma blue until it started to get dark and then rinsed it. I did this 4 times and then I followed up with 0000 steel wool and some gun oil to smooth out the perma blue and BAM, it looks awesome again. Took care of all the little scratches using the 0000 steel wool too.I normally don't get real excited about items, but this one I did. I fix 2 issues with one product. And it did what I would expect it to do.

Would have give 5 star but the directions on the bottle were in Spanish......I don't speak Spanish. Had to do an internet search to figure out how to use. Once I figured that out, it worked great.

Been using it for years