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Anyone done hot caustic bluing?

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  • #16
    Originally posted by DennisCA View Post
    I have never been able to find ammonium nitrate, not even come close, but from what I read it's for all purposes identical to AN based stuff and my results looked like regular hot caustic bluing to me.
    Probably won't find it anymore after that guy blew up the building in OK. Maybe if you know a farmer.

    JL................

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    • #17
      Originally posted by JoeLee View Post
      Probably won't find it anymore after that guy blew up the building in OK. Maybe if you know a farmer.

      JL................
      10 pounds of Ammonium Nitrate @ $25, delivered to your door:

      https://www.amazon.com/Instant-Cold-.../dp/B07CZK913Y
      Last edited by tlfamm; 09-22-2020, 03:50 PM.

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      • #18
        Originally posted by JoeLee View Post
        Probably won't find it anymore after that guy blew up the building in OK. Maybe if you know a farmer.

        JL................
        Or, just go to Home Depot or Lowe's or somewhere... buy a sack of 34-0-0 fertilizer.

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        • #19
          Originally posted by nickel-city-fab View Post

          Or, just go to Home Depot or Lowe's or somewhere... buy a sack of 34-0-0 fertilizer.
          How pure does the AN need to be in order to work right?

          Bagged fertilizer probably has something else mixed in it to help control the application rate, maybe bentonite or something similar to pelletize the AN in a somewhat "diluted" form. And to control it's suitability for "other uses". Possibly other materials to help control various properties for application.
          1601 2137 5683 1002 1437

          Keep eye on ball.
          Hashim Khan

          If you look closely at a digital signal, you find out it is really analog......

          Comment


          • #20
            Originally posted by tlfamm View Post

            10 pounds of Ammonium Nitrate @ $25, delivered to your door:

            https://www.amazon.com/Instant-Cold-.../dp/B07CZK913Y
            Followed by a knock at the door!

            JL..........

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            • #21
              Originally posted by JoeLee View Post

              Followed by a knock at the door!

              JL..........
              Nobody has knocked yet ...

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              • #22
                Originally posted by J Tiers View Post

                How pure does the AN need to be in order to work right?

                Bagged fertilizer probably has something else mixed in it to help control the application rate, maybe bentonite or something similar to pelletize the AN in a somewhat "diluted" form. And to control it's suitability for "other uses". Possibly other materials to help control various properties for application.
                I was following a discussion about this on some gunsmithing forums, and the conclusion was that the fertilizer was OK, might take a bit longer is all. One of their guys was trying it. But that was back in 2012 or thereabouts.

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                • #23
                  You can't ammonia nitrate at HD or Low's any more. Even ice packs are moving away from it. Here is a place to get it online: https://ammoniumnitrateforsale.com/main.sc .

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                  • #24
                    Started with potassium nitrate blackening today. Getting the nitrate from stump remover, which I found some of in the shed.

                    Put in something over 10 g of the material, heated the solution and the part in it. The part had been cleaned with purple cleaner. Container is an old SS cooking pot.

                    After 45 minutes, the solution was a brownish tint, with a hint of some scum, but the part had only a few "spots" where there was a sort of gray discoloration.

                    The source for this idea was https://bbs.homeshopmachinist.net/fo...ide-experiment

                    Is the AN the only stuff that works for this?
                    1601 2137 5683 1002 1437

                    Keep eye on ball.
                    Hashim Khan

                    If you look closely at a digital signal, you find out it is really analog......

                    Comment


                    • #25
                      Originally posted by SLK001 View Post
                      You can't ammonia nitrate at HD or Low's any more. Even ice packs are moving away from it. Here is a place to get it online: https://ammoniumnitrateforsale.com/main.sc .
                      News to me -- https://www.homedepot.com/p/Scotts-T...61-1/302688123
                      Then there's Lowe's and Ace hardware...
                      Different brands, same chemicals.



                      Last edited by nickel-city-fab; 09-25-2020, 05:00 AM.

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                      • #26
                        Originally posted by nickel-city-fab View Post

                        News to me -- https://www.homedepot.com/p/Scotts-T...61-1/302688123
                        Then there's Lowe's and Ace hardware...
                        Different brands, same chemicals.


                        The chemical in these products is UREA, which CANNOT be used to make a bluing solution.

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                        • #27
                          Originally posted by J Tiers View Post
                          Started with potassium nitrate blackening today. Getting the nitrate from stump remover, which I found some of in the shed.

                          Put in something over 10 g of the material, heated the solution and the part in it. The part had been cleaned with purple cleaner. Container is an old SS cooking pot.

                          After 45 minutes, the solution was a brownish tint, with a hint of some scum, but the part had only a few "spots" where there was a sort of gray discoloration.

                          The source for this idea was https://bbs.homeshopmachinist.net/fo...ide-experiment

                          Is the AN the only stuff that works for this?

                          10 grams? That's about 1/3 of an ounce. KNO3 might work, but with this small of a quantity, you'll need to get your mixture perfect. Also, using a SS pot is said to poison the mixture (because of leeching?).

                          NH3NO3 works and so does NaNO3.

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                          • #28
                            Originally posted by SLK001 View Post


                            10 grams? That's about 1/3 of an ounce. KNO3 might work, but with this small of a quantity, you'll need to get your mixture perfect. Also, using a SS pot is said to poison the mixture (because of leeching?).

                            NH3NO3 works and so does NaNO3.
                            Ummmmm..... Not YOUR formula, but the straight ammonium nitrate version (just using potassium nitrate as recommended) in the link shown. Check the link (extract below)

                            Originally posted by markx View Post
                            Perhaps this be interesting for some viewers here....

                            I have been doing some development work on black oxide coating process to apply a visually appealing appearance to the machined steel parts. The classical approach for a hot blackening bath usually involves saturated solutions of lye and nitrate with some additives like nitrites. Although it works well and gives a durable finish I do not like the highly corrosive composition and hot temperatures involved in the process. Spill the contents of the hot bath and all hell shall break loose.
                            So perhaps it can be done in milder conditions and with less danger of permanent chemical burn.....

                            I propose the following bath composition:

                            Ammonium nitrate : 10g
                            Distilled water : 1000ml (1L)

                            *AN content is not critical, bath remains operational from 1-15% AN content by mass (10-150g per liter), but higher AN content causes more instability and sidereactions.


                            Optional accelerators for the bath:

                            Option A- Potassium or sodium chlorate : 160-240mg /1L
                            Option B- Potassium or sodium perchlorate: 400-800mg/1L

                            The bath operates with ferrous alloys at boiling point of water or slightly lower (95-100C) due to the dilute solutions and has no caustic components that can cause chemical burn or damage the surroundings when spilled. A decent black coating is obtained within a timeframe of 5min (for simple carbon steels) up to 2 hours (for heavily alloyed tool steels). The coating time is individual for each alloy, but usually 30-40min shall guarantee a nice coverage for most ferrous alloys. The accelerators are optional and do not have to be included into bath composition. They do provide faster oxide coverage of some alloys and slightly impart on the coloration of the coating (bluish purple coatings can be obtained, but the effect is a bit vague). For simplicity sake they can be left out of the composition.....as when overdosed the acceleration effect is reversed and oxide formation is slowed significantly. That is especially true for "Option A", upon overdosing of chlorate the bath becomes inert.

                            Regarding plating vessel material and storage of the plating solution:

                            Stainless steel is best. Aluminium could theoretically be used, but I have not tried it. A.....................
                            1601 2137 5683 1002 1437

                            Keep eye on ball.
                            Hashim Khan

                            If you look closely at a digital signal, you find out it is really analog......

                            Comment


                            • #29
                              Originally posted by J Tiers View Post
                              Started with potassium nitrate blackening today. Getting the nitrate from stump remover, which I found some of in the shed.

                              Put in something over 10 g of the material, heated the solution and the part in it. The part had been cleaned with purple cleaner. Container is an old SS cooking pot.

                              After 45 minutes, the solution was a brownish tint, with a hint of some scum, but the part had only a few "spots" where there was a sort of gray discoloration.

                              The source for this idea was https://bbs.homeshopmachinist.net/fo...ide-experiment

                              Is the AN the only stuff that works for this?
                              What was your boiling point?? gray discoloration is usually a sign on the bath not being hot enough and oil or solvent film still on your parts.

                              I always clean my parts in lacquer thinner, it cuts everything and evaporates fast. If the part fails to take the blue then I etch it in muriatic acid, wash it off and then go to the thinner wash.

                              How ever with all these back yard concoctions I have no idea where the optimal temperature would be. Are the chemicals your using pure?? do they contain other additives that may hinder the process. a lot of unknowns there.

                              I just did a batch yesterday, everything came out perfect as usual except for some old wood screws that were bare steel. they didn't take at all. I gave them a quick dip in the muriatic acid and tried again. they came out perfect, must have been some petina that the thinner wouldn't remove. There was also one 1/4" machine screw that didn't take at all, while all the others from the same machine did. I thought it might have been stainless. I gave that one a muriatic dip also and it came out perfect.

                              Even the commercial salts contain other elements.

                              One other thing to take into consideration is your water source??? What minerals might it contain?? and what are their percentages. This might sound like were going too far but it can make a difference. Also.......... I wouldn't advise using distilled water.

                              JL................
                              Last edited by JoeLee; 09-25-2020, 12:42 PM.

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                              • #30
                                @JoeLee: "I wouldn't advise using distilled water"

                                ???

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