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Thread: Black oxide experiment

  1. #41
    Join Date
    Mar 2018
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    Finland
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    183

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    Here is the recipe I have used for phosphating, scaled to a small batch:

    500ml distilled water
    42.5ml 30% phosphoric acid (in finland Motonet has rust remover that is this concentration, hence the uneven number, was converted from something imperial I think, this is from 2010)
    10g manganese dioxide (got it from a battery, I also have a jar now of this powder from an arts store)
    steel wool 2.5 grams





    Part then goes into oil.


    It never gets as dark as bluing does. Always a kind of dark grey at most.

  2. #42
    Join Date
    Sep 2008
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    WI/IL border
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    I just found and bought 5lb of AN here: https://www.ammoniumnitrateforsale.com. It's also sold at Amazon, but in larger quantities.



    I'll use it for experimentation related to instant ice packs, and the leftovers can become a lifetime supply for blackening.

    Thank you for the procedure description, Markx. I want to try it and compare with rust blackening for those heat treated parts where I cannot use my staple, the burnt oil method. Can you comment of the rust preventing property of the black layer left by the AN procedure? Do you need to constantly re-oil the parts to prevent rust? Do the blackened parts with no oiling (or after a single initial oiling) hold a way better than bare steal with a comparable oiling regimen?
    Last edited by MichaelP; 11-16-2018 at 01:36 AM.

  3. #43

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    Quote Originally Posted by MichaelP View Post
    I just found and bought 5lb of AN here: https://www.ammoniumnitrateforsale.com. It's also sold at Amazon, but in larger quantities.

    [LIST][*]
    Thank you for the procedure description, Markx. I want to try it and compare with rust blackening for those heat treated parts where I cannot use my staple, the burnt oil method. Can you comment of the rust preventing property of the black layer left by the AN procedure? Do you need to constantly re-oil the parts to prevent rust? Do the blackened parts with no oiling (or after a single initial oiling) hold a way better than bare steal with a comparable oiling regimen?
    You are welcome, I'm glad someone finds the method useful. As for the rust prevention ability, it sure is improved upon comparison to bare oiled steel. I made some preliminary improvised tests on utility knife blade sections (SK-5 carbon steel) I used to test the bath compositions (they are uniform and very suitable to bring out any differences). The coated and oiled part was immersed halfway into room temperature sodium chloride solution for a time and the formation of corrosion observed. All in all the parts resisted visible rust formation in these conditions for about 24 hours. After that there was visible brownish residue forming in the solution and corrosion could be observed at the meeting point of air and salt solution. Obviously this is the most agressive point, the contact surface where all factors that promote corrosion are there: oxygen, water and salt. At the section that was submersed there were no visible rust formations, neither at the section that was not submersed. The coating remained in tact, but one could see a surface texture difference between the areas that were submersed and not. For one test I left the knife blade in the salt solution for about a week: contact surface was heavily pitted, but the rest was quite ok, some small pits on the submersed area, but the coat remained in tact.
    I have not tested against commercial oxide coating in same conditions, so I can not yet comment on that.
    As for just ageing the coated parts in room temperature I have not observed any rust formation on any of them really....neither on the parts that are used and handled by the lathe (tailstock extensions, tool holders). When the parts were uncoated, they formed visible rust on them quite fast from the handling and moisture in the air. So it seems to be an improvement, although it is no miracle cure against corrosion. Constant oiling is not required, but an occasional swipe with a oiled rag is not going to harm. The parts on the lathe contact cutting oil anyways, so I just wipe them clean from time to time.

  4. #44

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    Quote Originally Posted by gambler View Post
    with a cool star on his chest. but no, the other kind.
    I trust You mean that smaller breed of dog then:






    It is made from a high carbon hex bar and designated to turning of 20mm (0,8in) shafts, barrels or pipe between the centers. The tail is stainless steel and thread fitted. Turned out pretty cool I think...

  5. #45
    Join Date
    Jun 2009
    Location
    san jose, ca. usa
    Posts
    810

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    I agree, very cool design, consider the idea stolen. thanks

  6. #46
    Join Date
    Aug 2009
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    Well, am I going to be accused of stealing the idea also ????

    I came up with the idea during the summer before I ever saw anything like the one above. I came up with it as a way to rotate this dead center so I could re-grind the taper.
    It's just a natural way of thinking with stuff like this.
    Mine is a set screw collar with a dowel pin for the drive contact.

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

    Last edited by JoeLee; 11-16-2018 at 12:30 PM.

  7. #47
    Join Date
    Sep 2008
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    Thank you for the clear answers, Markx. I like this kind of approach to testing/investigating. It's rare nowadays.

    About the dog. Why did you choose a hex vs. round? Just for esthetics / material availability or it serves a specific purpose?
    Last edited by MichaelP; 11-16-2018 at 04:08 PM.

  8. #48
    Join Date
    Jun 2009
    Location
    san jose, ca. usa
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    you guys are both innovaters

  9. #49

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    Quote Originally Posted by MichaelP View Post
    Thank you for the clear answers, Markx. I like this kind of approach to testing/investigating. It's rare nowadays.

    About the dog. Why did you choose a hex vs. round? Just for esthetics / material availability or it serves a specific purpose?
    I have a bootload of hex available and I thougt it would look better for some reason.....really there is no practical purpose behind the geometry. A round bar or any other geometry would deliver pretty much the same performance.

  10. #50

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    See if we can etch a polished surface with the AN bath.....


    A freshly polished SK-5 blade


    Into the bath and immediately developing a coating


    Going through some very pretty lilac tones as the magnetite layer grows



    After 40 min of simmering in the bath....it is basically a mirror finish (the reflecion of my fingertips on the blade should be pretty visible)

    It s actually very hard to get a good shot of this surface...it is dark and reflective

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