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More details on the sealing process, please

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  • More details on the sealing process, please

    I'm still absorbing information as quickly as I can. I realized the other day that I really have no understanding of the sealing process. As I understand it, it is used to seal the pores of the hexagonal tubes formed during anodizing... but how? Are they sealed with another layer of aluminum oxide? What exactly is happening in the boiling water, chemically and physically?

    Thanks again!

  • #2
    Sealing by heat; usually boiling water or very saturated steam, forms a hydrous aluminum oxide film. Water is necessary for this reaction to proceed (dry heat won't work). The temperature of this reaction is below but close to the boiling point of water. This form of aluminum oxide is less dense than the anodize, hense it takes up more space, and fills the pores. The hydrous Al oxide forms on the outer surface and in the pores, it doesn't normally displace any dye in the pores. As it forms, it plugs up the open end of the pores. Being aluminum oxide, it is as chemically inert as the anodize, but a little softer.

    IMHO; this method of sealing is superior to chemical sealing, which plugs up the pores with a chemical precipitate, which is not as inert. Heat sealing (more accurately wet heat sealing) however, takes longer to do, and has a higher fuel cost.


    • #3
      Thanks Fiber, that's what I was looking for. mmmmm yummy knowledge! :P