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  • Faliure at anodizing two pieces at a time

    Hello everybody.
    I tried anodizing two pieces at the same time. First try was hanging both pieces from the same aluminium wire and connecting the positive half way. For the second attempt I use a copper rod (1/4 inch) with two holes, which I used to hang the pieces. (positive was screwed to one end of the rod)
    I´m pretty sure connections all the way were solid.

    I added the surface area of both pieces and used the 720 rule (which unsurprisingly was the double amps. of a single piece)

    In both test, only one piece got anodized (although they were cooked!) and the other is like it was never anodized! Taking zero dye.

    I even took both of the non-anodized parts and redo them individually and result were perfect.

    Again Im pretty confident my connections were OK.

    Any ideas/advice

    Thanks

  • #2
    First, never, ever, ever use copper in the acid bath. Copper will contaminate the bath and will raise its conductivity to a point that everything you try to anodize will burn.

    Now to the problem. If the connections were solid as you say, then just about the only other thing that could cause this would be running different incompatible alloys. To a small extent you could see this if your cathodes were very close to one part, and very far from the other. Unless it's extreme though, you would not see one part have nothing on it.

    This really smells of a bad connection on one part. If it's still happening, after you rack the parts, use an Ohm meter to measure the connections before putting them in the tank. If you measure nearly 0 Ohms between one part and the other, then both parts will have a good connection.
    Process control doesn't give you good quality, it gives you consistent quality.
    Good quality comes from consistently doing the right things.

    Process control systems for anodizers
    If a post helps you out spread the love and LIKE the post
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    Last edited by kevinB: Now. Reason: superfluous typo's

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