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maintaining wire flexibility after anodizing

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  • maintaining wire flexibility after anodizing


    I was hoping that somebody in this forum may be able to help me out with my problem. I am doing some anodizing for a jeweler who works with thin wire. It is 5657 alloy (i think) which is mainly used for aluminum soldering. She has been using it for a while, but i wanted to improve the overall production (i.e color after dying, shininess). So I have made a new tank and setup which works great. The color of the metal is fantastic after dying, but unfortunately the metal is too brittle for her needs.

    I have been anodizing at 3-5 Amps @12V using a battery charger. The electrolyte solution is diluted sulfuric acid in distilled water. The anodizing time which produced the best color was 3 hrs. My dilemma is that I want to maintain the color quality while allowing the metal to be flexible enough for bending. I understand that the aluminum oxide layer produced by anodizing is quite brittle, so reducing time in the tank may improve the flexibility (at the cost of color quality). However, I was wondering if sealing may also affect the brittleness. I seal in steam for 30 min. Then sometimes put the metal in an oven for 30 min @ 200F. The heating in the oven sometimes improves flexibility, sometimes does not.

    I would love any advice from the audience here. Any suggestions would be very much appreciated as I am kinda stuck. Please help!!



  • #2
    Anodizing aluminum at real high current density will also make it very brittle. Your 5657 alloy is used for MIG welding aluminum not soldering, like other 5xxx series alloys it does anodize well.

    If your 3-5 amps is actually correct (doubtfull if your are reading it on the "ammeter" of a battery charger) the wire would have to be very long and a very large diameter to not be being at way too high a current density. If you provide the length and diameter of the wire the current density can be easily calculated.

    If you're interested in anodizing the right way, download and read this: