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Posted: 10/25/2024 1:26:33 PM EDT
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I always thought it could not be done to stainless, but apparently it can with the right chemicals. I have done a couple pistols in traditional holt salt bluing using a old ammo can that was sand blasted as my tank, and a turkey fryer to heat it (candy thermometer to monitor temp) and had really great results. I used the chemicals from EPI. I was looking and they also have a solution for stainless steel. https://www.epi.com/black-oxide-products/chemicals-by-substrate/stainless-steel.html I have a few small stainless parts I want to blacken and was thinking about trying it. Just curious if anyone here has done it. |
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Brownell's sell a special bluing chemical that can do gun type stainless bluing. Firearms stainless has a higher carbon content then other stainless's. There were a few refinishers who offered stainless bluing but most stopped due to customer complaints about the color and lack of durability. It's not an easy job and it takes some experimentation to get it right. Even then getting a consistent color is difficult. I haven't seen any work done with the EPI but as far as a "bluing" chemical, the hot salts Brownell's is usually the best. https://www.brownells.com/tools-cleaning/paint-metal-prep/metal-bluing/oxynate-no.-84---hot-bluing-salts-compound/ |
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Quoted: Brownell's sell a special bluing chemical that can do gun type stainless bluing. Firearms stainless has a higher carbon content then other stainless's. There were a few refinishers who offered stainless bluing but most stopped due to customer complaints about the color and lack of durability. It's not an easy job and it takes some experimentation to get it right. Even then getting a consistent color is difficult. I haven't seen any work done with the EPI but as far as a "bluing" chemical, the hot salts Brownell's is usually the best. https://www.brownells.com/tools-cleaning/paint-metal-prep/metal-bluing/oxynate-no.-84---hot-bluing-salts-compound/ Yea I saw the brownells stuff, but sadly they only sell it in the 40lb pail. I do not need that much. I have used the EPI ultra black 400 and it worked great. I bought the 10lb bottle and still have half of it left. Looking at the MSDS sheets for each. The EPI ultra black 400 I have is mainly Sodium hydroxide with smaller amounts of Sodium nitrite (looks like 2 different types) and a small amount of Ethylene thiourea. The EPI ultra black 407 (for stainless) is less Sodium hydroxide and more Sodium nitrite, and a little Potassium dichromate. The brownells no-84 looks like it is the same mixture of SH and SN as the EPI 407 with "Other components below reportable levels" instead of the PD. Luckily EPI sells as low as 1lb "sample" bottles of their stuff so you can try it out, and I think that would be enough to do the few small parts I want to do. MSDS sheets if you are curious: Ultra black 400 for carbon steel Ultra black 407 for stainless Brownells No 84 |
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Ok, long post. The factory bolt has a kinda rough texture to it. If I had to guess, it would say it looks like the parts were tumbled in a ceramic media. I did a light polish of the parts to try and get a more gloss blue finish like the rest of the parts. Here you can see the bolt shroud untouched, compared to the breech block I lightly polished.  Parts polished and ready to go:  I went to harbor freight and bought a 30 cal ammo can, sandblasted the inside to use as a tank. I do not know what paint they use, but holy crap it is tough! After sandblasting on it for a long time in my blast cabinet, and barely getting anywhere, I ended up using a torch to burn the paint off and then sandblast the inside again. I cleaned in acetone, then followed their instructions. I used their e-kleen SR102E to clean again, rinsed, then dipped in 50-50 mix of water and muriatic acid, rinsed, then dipped in the solution for around 5 min. Temp maintained at 250-260 and boiling the whole time, as needed. Rinsed and used the water displacing oil.   Result was good and not good. Parts looked good, but a couple spots it did not take. One corner of the bolt shroud was not coated, and the bolt handle looked a little thin. I cleaned, degreased, and then dipped the parts again for a little longer with no change.    I contacted EPI and sent them some pictures and asked what I may have done wrong and if they had any pointers or recommendations. They said to make sure to use steel wire and not stainless or anything else. They also asked if I polished and that polished parts are harder to blacken and I may have to roughen them up slightly. They also said to try 90% acid and leave it in for longer (5-10 min), and then leave in the blackening solution for 10-20 min. Well I had used stainless wire as I figured that would work fine, since the parts were stainless. But I guess not. I then tried to blast the parts with baking soda but it was just too gentle. I ended up turning the pressure way down and using my blast cabinet and doing a very gentle blast. I repeated the process all over again following their tips and had no spots left uncoated. However the parts turned out a little more grey. The bolt handle also still seems thin and is thin on the corners/edges. I polished the bolt body as it move in the receiver and I wanted that smooth and was surprised as just how easy the black came off. I do not think this finish is going to hold up to normal use.   So all in all, I am going to call this a failure. For the money/time spent, and the results I got, this venture was not worth it. I should have sent the parts to get cerakoted in their "midnight blue" that is supposed to look very close to bluing. I place no blame on EPI chemicals, they have been great, and I used their ultra-blak 400 on a carbon steel pistol a couple years ago with perfect results and it still looks good today. I think I would have gotten the same results with the brownells solution. Maybe these parts and/or specific type of metal just do no blacken well. |
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Good informative post. This is apparently why most refinisher services stopped bluing stainless. It was not as durable as people expected, and not as dark as wanted. In addition, getting uniform jobs was difficult even with experience. There are other ways to give stainless a true black color and a durable finish, but it seems most are not something a hobbyist can do at home. One technique would be to iron plate stainless and gun blue that. Caswell also sell black chrome plating kits, but black chrome is not very durable at all. Lacking a good black finish of some sort, I'd consider a bead blast finish similar to Ruger's Terhune Target Gray finish. |
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