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Thread: Corrosion on anodised Al

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    RBW Member rian jordaan will become famous soon enough rian jordaan will become famous soon enough rian jordaan will become famous soon enough rian jordaan's Avatar
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    Corrosion on anodised Al

    Made a part out of 6086 Aluminium which I had anodised to a matt black finish @ 20microns thick. Wet sodasorb got wedged between surfaces and boy did this create havock. Needless to say the O-ring doesn't seal any more.
    Any body out there that knows why?

    I know that the surface of Al gets cleaned with cold caustic solution prior to anodising and that a mild solution of caustic will dissolve the anodising. So I take it that anodised surfaces and solutions of high Ph values don't go together. Does the big manufacturers use a special grade or type of anodising?

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    Re: Corrosion on anodised Al

    There are a variety of anodizing processes for a particular application,
    check out this link, for more information.

    What is Anodizing?

    Sorb is " exothermic"
    Remember... wet sorb + alum. = drano ( very caustic ).

    Hope this helps.

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    Re: Corrosion on anodised Al

    The sodium hydroxide in sorb will eat anodizing and aluminum. Thicker anodizing like Mil Type III will just prolong the inevitable.

    Sorb water and aluminum just don't get along, and the aluminum always loses.

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    RBW Member rian jordaan will become famous soon enough rian jordaan will become famous soon enough rian jordaan will become famous soon enough rian jordaan's Avatar
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    Re: Corrosion on anodised Al

    Any other sugestions on products that I can use?
    I had a look at ceramic coating but a bit expensive. I need a stable "paint" where the O rings can seal.

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    Re: Corrosion on anodised Al

    Quote Originally Posted by rian jordaan  View Original Post
    Any other sugestions on products that I can use?
    I had a look at ceramic coating but a bit expensive. I need a stable "paint" where the O rings can seal.
    Switching material might be the better alternative.

    Chemical resistant plastics work the best. Most common plastics are chemical resistant to sorb water. Acetal, copolymer, ABS, Nylon, Polypropylene.

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