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Thread: Is this true silicon bronze?

  1. #1
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    Default Is this true silicon bronze?

    I recently purchased silicon bronze wood screws at a (I think) reputable retailer in the greater Toronto area. The retailer was recommended to me by Tendercraft. I was shocked at how little they cost as compared to a quote I received at a national retailer, so I bought some and ran a test. In the attached image, the screw on the left was submerged in a strong salt solution for two weeks while I was on vacation. Obviously the colour has changed, but is that what should happen, or should I still have a shiny screw? I'm wondering if they are selling me true silicon bronze, or if the original retailer just has really high prices ($2.45 CAD for one 12x3' SB wood screw).

    screws.jpg
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    Last edited by einheldenleben; 07-25-2021 at 12:14 PM.

  2. #2
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    Default Re: Is this true silicon bronze?

    For reference Hamilton Marine sells 12x3 bronze screws for US$2.29. Or $149 for a hundred.

  3. #3
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    Default Re: Is this true silicon bronze?

    Yes, I was thinking that...also noticed "Naval Bronze" in their catalogue.

  4. #4
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    Default Re: Is this true silicon bronze?

    The logical options are bronze or brass.
    I have heard it said that if you drop the two on a concrete floor the bronze will have a nice clear tone of a ring, and the brass will have a bit of a duller sound. That has seemed to prove itself out when I have done it, and have sorted screws this way. Of course you need one of each to start out with.

  5. #5
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    Default Re: Is this true silicon bronze?

    nedL, I tried that on a stone tile floor, and it's decidedly more of a dull "tink" rather than a clear ringing pitch. I am growing more skeptical about what I was sold. I also forgot to mention that I purchased some Si Bronze ring nails, and they have a distinctly more dark coppery colour to them.

  6. #6
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    Default Re: Is this true silicon bronze?

    Likely not bronze. Also the shank is thinner than the one on the left.
    Bronze fasterners are horrifically expensive these days. Suggestions: 1. Get a real wholesale account at a for real supplier, not these bogus hobbyist places. Try Fisheries Supply...going to be cheaper unless you are just doing onesy and twosies. 2. I prefer lathe cut fasteners rather that stamped threads. 3. And of course, use square drives.

  7. #7
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    Default Re: Is this true silicon bronze?

    Silicon bronze fasteners look exactly like copper, not "yellow"
    "Everdur" is 95% copper (used for casting, weldments etc)
    Alloy #C65100 is 98.5% copper, this is typical for fasteners
    See: https://atlasmetal.com/copper-alloy-c65100.php
    I suspect the sound it makes when hitting the floor has more to do with the "hardness" than anything else

  8. #8
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    Default Re: Is this true silicon bronze?

    The only way to know for sure is to have them tested, so fire up your favorite search engine and see how much it costs. Nowadays you can even rent a portable XFR machine and test every single screw right on the counter in the store, before you buy them.

  9. #9
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    Default Re: Is this true silicon bronze?

    Silicone bronze is nearly all copper. So it looks like copper. As far as i know.

    The one on the right in the picture looks more like brass to me - which is about 1/3 zinc. The thing to watch for in brass is galvanic corrosion.

    Can anyone confirm if my thinking here is correct;
    As an experiment, screw one into a piece of mild steel and stick it back in the salt water - see what happens. Not sure how you'd add a low current safely.
    If brass the screw aught to get eaten first, if silicone bronze the mild steel aught to go more rapidly.
    It's all fun and games until Darth Vader comes.

  10. #10
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    Default Re: Is this true silicon bronze?

    In the past I have sourced bronze screws successfully from :

    1. Jamestown Distributors
    2. A tiny outfit in Minneosota (canīt recall their name, but Google for a supplier in Minn.
    3. Bolt Depot in Boston

    Yes, Bronze screws have gone through the ceiling !

  11. #11
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    Default Re: Is this true silicon bronze?

    The silicon bronze that I have, which I know for certain is SB is yellow, not copper. By contrast, the phosphor bronze that I bought from the same source is much more copper colour.

    Brass, after the zinc has corroded out, does turn copper colour.
    It really is quite difficult to build an ugly wooden boat.

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  12. #12
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    Default Re: Is this true silicon bronze?

    Melt one with a welding torch. Brass will sputter and give off a lot of toxic white gas as the zinc cooks off. Bronze will melt into a nice round globule with little gassing.

    Stay upwind.

    Jim

  13. #13
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    Default Re: Is this true silicon bronze?

    Quote Originally Posted by Rumars;[URL="tel:6492261"
    6492261[/URL]]The only way to know for sure is to have them tested, so fire up your favorite search engine and see how much it costs. Nowadays you can even rent a portable XFR machine and test every single screw right on the counter in the store, before you buy them.

    I took this in to have an XRF test done at a gold shop. See results below. The machine apparently only detects metals, so that would explain why silicon is not listed. The copper amount certainly seems way too high to be Si bronze, but on the other hand no Zinc was detected, which should be present in abundance if it were Brass. Inconclusive, but would appreciate thoughts
    .F9709ABC-C019-4BE3-AB46-C50617E5C2E0.jpg
    Last edited by einheldenleben; 07-26-2021 at 03:43 PM.

  14. #14
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    Default Re: Is this true silicon bronze?

    Either that is a nearly pure copper screw (unlikely I think?), or the 'percentages' don't take what it can't measure into account. Silicon Bronze should be something like 96% Cu by weight. The rest is Silicon, plus some odds and ends. If that machine is ignoring silicon, it very well may be Silicon Bronze.

    Of course, that assumes it would have picked up on the Zinc. If you get back to that tester, maybe throw a known bit of brass at it to see what it says. Or even better, a known Silicon Bronze sample. At the very least, a Zinc coated faster would confirm it does read zinc?

  15. #15
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    Default Re: Is this true silicon bronze?

    Just for fun, see if it is attracted to a magnet.
    Quote Originally Posted by James McMullen View Post
    Yeadon is right, of course.

  16. #16
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    Default Re: Is this true silicon bronze?

    Quote Originally Posted by lukes View Post
    Either that is a nearly pure copper screw (unlikely I think?), or the 'percentages' don't take what it can't measure into account. Silicon Bronze should be something like 96% Cu by weight. The rest is Silicon, plus some odds and ends. If that machine is ignoring silicon, it very well may be Silicon Bronze.

    Of course, that assumes it would have picked up on the Zinc. If you get back to that tester, maybe throw a known bit of brass at it to see what it says. Or even better, a known Silicon Bronze sample. At the very least, a Zinc coated faster would confirm it does read zinc?
    According to this brochure the machine is supposed to detect all the metals, including Zinc, and they have screenshots on their website showing alloy composition breakdowns showing "Zn," so I think it's safe to assume it's not brass. I had the same thought about going back with a known Si Bronze sample to compare. And yeah, I don't think it's a pure copper wood screw. I've never heard of such a thing, but ya never know.

  17. #17
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    Default Re: Is this true silicon bronze?

    Quote Originally Posted by Canoeyawl View Post
    Silicon bronze fasteners look exactly like copper, not "yellow"
    "Everdur" is 95% copper (used for casting, weldments etc)
    Alloy #C65100 is 98.5% copper, this is typical for fasteners
    See: https://atlasmetal.com/copper-alloy-c65100.php
    I suspect the sound it makes when hitting the floor has more to do with the "hardness" than anything else
    I'm assuming I have something like the 65100...basically just a bunch of copper with a tiny amount of silicon added.

  18. #18
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    Default Re: Is this true silicon bronze?

    I dunno... I always thought bronze should have at least a bit of Tin (Sn) in it, but I guess that's not the case.

    Bronze?_Really?.jpg

    This sample, with a small percentage of Manganese (Mn) but the rest is Copper (Cu) I guess is some flavor of bronze but I'd question it being sold as Silicon bronze. 99.64 + 0.36 = 100.00, right? Where's room for any Silicon?

    Here's a few examples of Silicon bronze suppliers who publish the compositions of the alloys they sell under that classification:

    http://www.supermetalind.com/product...ilicon-bronze/

    https://www.concast.com/files/C65100.pdf

    https://www.makeitfrom.com/material-...-C65100-Bronze

    Given the recent rise in the price for copper worldwide I'd expect to pay a premium for anything whose composition includes a high percentage of it but labeling then selling something that's not what it truly is?

    Not a vendor I'd choose to continue doing business with.

  19. #19
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    Default Re: Is this true silicon bronze?

    XRF machines can and do detect Si, even one specialized for jewelry should do it. It says this is a high copper alloy, not a bronze or brass.
    You can repeat the test with a more "industrial" machine, but I highly doubt the result will be entirely different.

  20. #20
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    Default Re: Is this true silicon bronze?

    Quote Originally Posted by sp_clark View Post
    I dunno... I always thought bronze should have at least a bit of Tin (Sn) in it, but I guess that's not the case.

    Bronze?_Really?.jpg

    This sample, with a small percentage of Manganese (Mn) but the rest is Copper (Cu) I guess is some flavor of bronze but I'd question it being sold as Silicon bronze. 99.64 + 0.36 = 100.00, right? Where's room for any Silicon?

    Here's a few examples of Silicon bronze suppliers who publish the compositions of the alloys they sell under that classification:

    http://www.supermetalind.com/product...ilicon-bronze/

    https://www.concast.com/files/C65100.pdf

    https://www.makeitfrom.com/material-...-C65100-Bronze

    Given the recent rise in the price for copper worldwide I'd expect to pay a premium for anything whose composition includes a high percentage of it but labeling then selling something that's not what it truly is?

    Not a vendor I'd choose to continue doing business with.

    Quote Originally Posted by Rumars View Post
    XRF machines can and do detect Si, even one specialized for jewelry should do it. It says this is a high copper alloy, not a bronze or brass.
    You can repeat the test with a more "industrial" machine, but I highly doubt the result will be entirely different.

    This site reviews the Olympus GoldXPert XRF machine. They say: "The one item we tested which showed 100% gold was a computer CPU chip with a layer of gold on its back. Now you know why recycling used electronics can be a profitable business. However, the computer chip sample did raise some questions for us. Clearly the chip was not solid gold, yet the analysis did not show any other elements. We asked and were told that the GoldXpert was calibrated to detect metals, so elements such as silicon (the primary substrate for chips) would not be detected."

    I'm guessing that in my case, it is not detecting the silicon either and just lumping it in with copper. The thing that is confusing the hell out of me is even if the screws indeed are just pure copper, they should still be selling them for 2-3x more than they currently are. What's the catch? Anyway, thanks to everyone for the ideas and input. I think I know enough to move forward. The fastener retailer has good reviews and a good reputation, and was recommended to me by a wooden boat shop which stocks their items. I have to put a bit of faith in them. I think I'm just gonna go back and straight up ask them why they are selling Si bronze under market value and see what they say. Judge the reaction and go from there.
    Last edited by einheldenleben; 07-26-2021 at 11:20 PM.

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