Bonding Anodized Aluminum? - Page 2
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  1. #21
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    I'm definitely curious what Boeing came up with. You say as long as moisture can't get to the area. It sounds to me like that means moisture can't get to the adhesive at all, right? I can see moisture getting to the edges of the bond/adhesive layer, but not further than that. I'm not understanding that. Does moisture, even on the edge of bond, cause the onset of failure of the entire bonded surface, like a chain of failure type deal?

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    Just call this company,Epoxy Technology Inc. We bonded thousands of 6061, disks together after being 'hard anodized'.
    The tech there will listen to your application requirements, and offer a few products. The sell small quantities ("Kits") to prove the process.

    Regards,
    Chris

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    Quote Originally Posted by ezduzit View Post
    For a very strong and permanent bond I would use 3M 5200 polyurethane adhesive after first cleaning with denatured alcohol.
    I thought about 5200 also. I haven't found anything that shit doesn't stick to, and it's strong.

    Stuff gets everywhere though, lol. I swear I can cut open a brand new tube and 2 seconds later it's on the bottom of my shoes...

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    Quote Originally Posted by Mot3s View Post
    I'm definitely curious what Boeing came up with. You say as long as moisture can't get to the area. It sounds to me like that means moisture can't get to the adhesive at all, right? I can see moisture getting to the edges of the bond/adhesive layer, but not further than that. I'm not understanding that. Does moisture, even on the edge of bond, cause the onset of failure of the entire bonded surface, like a chain of failure type deal?
    It was not possible from the demonstration to determine if the failure was edge corrosion, corroding as the strips were separated or if the corrosion was full penetrating. I suppose it would have been interesting to stop the test with the strips separated for half their length wait for the "cloud" to disperse and then pull again, but that was not done.

    I worked for an electronics manufacturer and we would seal our micro electronic packages to make them hermetic. The only ones that were truly hermetic were the welded ones. The epoxy seals only slowed the intrusion of other gases. Therefore, only gross leak checks were done on the epoxy sealed packages.

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    Quote Originally Posted by Mot3s View Post
    I'm definitely curious what Boeing came up with. You say as long as moisture can't get to the area. It sounds to me like that means moisture can't get to the adhesive at all, right? I can see moisture getting to the edges of the bond/adhesive layer, but not further than that. I'm not understanding that. Does moisture, even on the edge of bond, cause the onset of failure of the entire bonded surface, like a chain of failure type deal?
    My recollection from an article in Aviation Week is that the epoxy is cured under heat, 250 F if I recall. That would solve the moisture problem, and epoxy is chemically aggressive at that temperature, and molecularly bonds directly to the metal surfaces.

    When I worked in the Plastics Lab at RCA in the 1960s (making stuff that was literally going to the Moon), we cured many epoxies at 180 F.

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  9. #26
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    Quote Originally Posted by Fulcircleny View Post
    Just call this company,Epoxy Technology Inc. We bonded thousands of 6061, disks together after being 'hard anodized'.
    The tech there will listen to your application requirements, and offer a few products. The sell small quantities ("Kits") to prove the process.

    Regards,
    Chris
    Thanks. I emailed them and am awaiting a response. From what I've looked into, the type of anodize and sealing process plays a role as well on how good the bond will be.

    Given that we have to justify our manufacturing decisions for this project, I think I will explore torque capacity on the screw and compressive yield strength of 7075 relative to that clamping pressure (though I would doubt is an issue) then estimate the force it could take before overcoming the clamping and frictional force. For all I know I can put way more torque on the screw than I would have intuitively considered and can just slap epoxy in there and not even mention it in the report.

    I just simply don't understand the science of bonding to be confident in saying anything about it.

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    Quote Originally Posted by Mot3s View Post
    snipped a lot....

    I have a screw clamping the surfaces as well, but the extra insurance of adhesive is what I would like.
    Based on the above portion of the original post, what do you really expect the epoxy to do? How heavily stressed is the part?

    I ask this because if you are really just looking for extra insurance, go to the West Systems website and read the newsletters there that describe the many many projects that involve bonding aluminum and other materials. They even publish adhesion tests that you might extrapolate from for your project.

    If you are an engineering student this could spice up your written portion and make it look like you did some sure enough engineering.

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    Quote Originally Posted by Mot3s View Post
    Could somebody please help me solve this issue with how to confidently bond 7075 aluminum to aluminum? .
    Quote Originally Posted by thermite View Post
    Need greater strength? WELD them under an inert gas instead of soldering under oil.

    Heliarc -> MiG -> TiG. Been going on and getting better and better and easier and easier ever since Aluminium first went cheap and available.

    Any of that is "too difficult"?

    .
    Oopsie.....

    But thanks for the "soldering under oil" trick anyways.

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    Quote Originally Posted by henrya View Post
    Based on the above portion of the original post, what do you really expect the epoxy to do? How heavily stressed is the part?

    I ask this because if you are really just looking for extra insurance, go to the West Systems website and read the newsletters there that describe the many many projects that involve bonding aluminum and other materials. They even publish adhesion tests that you might extrapolate from for your project.

    If you are an engineering student this could spice up your written portion and make it look like you did some sure enough engineering.
    This will be a measuring device, so the stress is dependent upon the user, which shouldn't be much if they use it properly. I would like it to confidently hold 50 lbs or more in shear, which I think is absolute overkill. It would be a poor design though if it were accidentally dropped from 4-5 feet and then completely toast after that.

    Imagine a 2.5 inch long, .1875x.625 flat bar of which the end of it ( about 1 square inch) is fastened to another flat surface. This bar absolutely cannot budge after setting. This bar will likely be used to hold onto during operation so there will also be torque applied to the joint but shouldn't be more than 5-6 in-lbs under most aggressive use.

    This whole thing could be a case of, "oh you only need it to do that?? HAHA"

    Thanks! I will check that out. I am in search of the spice.

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    Quote Originally Posted by Bill Simmons View Post
    Adhesives may work as long as moisture can never get to the area.

    I was at an EAA meeting where a fellow gave a demonstration and talk about epoxy bonding of aluminum. The aircraft he was building used epoxy for much of the structure like wing assembly. He researched the subject and found boeing had a proprietary treatment process for similar attachments.

    He brought some strips of aluminum that had been bonded together with just good cleaning processes. The strips were about an inch wide, 2 feet long and perhaps .025 thick. The last inch was not glued. Two volunteers were brought from the audience and each given a pair of pliers and told to pull on each of the unglued ends. Nothing happened. Then he took a spray bottle filled with water and sprayed a finely atomized cloud at strips. There was immediate failure with the strips peeling apart and the adhesive separating from the aluminum. The failure was so quick that it looked like a hoax. He had some strips that had been treated by Boeing and extreme pulling would cause the adhesive to split, the desired failure mechanism. He asked would you want to fly a plane into cloud with out treatment. I don't know how he pulled it off, but he actually got Boeing to treat his parts for a reasonable fee.

    I do not know what the treatment is that Boeing uses but it prevents the rapid (almost instant) corrosion. This corrosion has almost no strength.
    That was probably Alex Strojnik:
    https://www.amazon.com/Low-power-lam.../dp/B0006YF3HA

    I have his series of books, he describes the Boeing solution, it involves plating
    IIRC

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