How Anodization Is Used To Make Pretty IPod Colors

What do those colorful iPod Nano cases have in common with sapphires? In both substances the color is not on the surface, but integrated in the structure of the material. As usually, [Bill Hammack] unveils the interesting concepts behind coloring metal through anodization in his latest Engineer Guy episode.

We’re not strangers to the anodization process. In fact we’ve seen it used at home to change the color of titanium camping utensils. [Bill] explains what is actually going on with the electrochemical process; touching on facts we already knew; like that the voltage range will affect the color of the annodized surface. But he goes on to explain why these surfaces are different colors and then outlines how anodized metals can be dyed. That’s right, those iPod cases are colored with dye that will not wash or scratch off.

Pores are opened when the aluminum goes through anodization. Those pores are filled with dye, then the metal is boiled in water which closes them, sealing in the color. Pretty neat!

26 thoughts on “How Anodization Is Used To Make Pretty IPod Colors

  1. Given the titanium reference in the article it should be noted that while this “pores are filled with dye” is true with aluminum anodization, the same does not apply to titanium.

    Titanium anodization does not employ dyes but rather attains different colors by varying the thickness of the titanium’s oxide layer. This is also the case for niobium.

      1. okay you caught me….I didnt watch the video. I do enough anodizing it wasnt really of any interest to me….I guess my comment is only useful to those who read hackaday articles and comments and didnt bother to sit through the video. Sorry.

    1. I can see how those dosing could come away with the impression that dyed is use to color titanium. While Bill could have done better with the segue from titanium to aluminum, he basically said what you said Although he didn’t specifically point out dye isn’t use with titanium, bit AIIRC he didn’t say it was either.

  2. Those pores are filled with dye, then the metal is boiled in water which closes them, sealing in the color.

    Boiling is one method but not widely used in industry because of the absolutely massive energy required to boil 1000 – 5000 gallon tanks of deionized water. What most vendors do is use a mid temperature nickel acetate seal rather than boiling water.

    The only problem of course is that you infiltrate nickel into the aluminum (on purpose) and then you have to deal with the waste stream. All told though, anodizing is MUCH friendlier on the environment than plating (heavy metals) or painting (anodizing is VOC free).

    Pretty next!

    I think you mean neat.

  3. “next” was the name of one of apples early computers that filled a strange and arguable non existent niche in the market for an expensive and powerful desktop computer that had an absolutely perfect black cube as its case, costing vast sums in manufacturing. I don’t think it was a typo.

    1. NeXT had nothing to do with Apple and ran its own proprietary OS. Steve Jobs founded it after he got kicked out of Apple way back when. The cubes also burned brilliantly due to the magnesium cases if you can manage to get one lit.


      “Period Number: 3
      Group Number: 13
      Group Name: none
      What’s in a name? From the Latin word for alum, alumen.
      Say what? Aluminum is pronounced as ah-LOO-men-em.”

      or maybe

      “From the Latin word “alumen” meaning “alum”. The ancient Greeks and Romans used alum in medicine as an astringent, and in dyeing processes.

      Atomic Number = 13, Atomic Mass = 26.98, 13 protons, 13 electrons, 14 neutrons.

      First isolated by Hans Christian Oersted of Denmark in1825.”

      Just because you feel like adding syllables does not make it correct.

      1. ^Because that extra “I” is extra important? Four syllables is not enough? Now that you mention it, I guess we could squeeze another “U” in there; it seems to be popular…

      2. Cyril,
        We are speaking American English, so your appeal to English authority misses the mark.
        More importantly, Davy himself coined the name aluminum. Also, aluminum is an accepted variation by the IUPAC.

  4. I’ve wanted to anodize some aluminium can tabs in rainbow colors for a while. I just watched the video and it doesn’t seem too hard. Research time!

    p.s. Neither of those laptops uses unibody construction.

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