How is coating with an oxide oxidation

  1. I looked up the word oxidize and one of the definitions is to make it an oxide which is what happens when iron gets rusty(even though there is also iron hydroxide in rust).

    Another was to coat with an oxide. Now how is coating with an oxide oxidation?

    Does it catalyze the oxidation by making it easier for oxygen to get to whatever is being oxidized without the oxide being reduced and if so is the speed of the reaction the same or faster?

    Does the oxygen from the oxide go to what is being oxidized so that more oxygen can come in and oxidize it faster with the oxide getting reduced?

    Does the oxide and whatever is being oxidized form an oxidized complex?

    examples:

    Iron oxide coating on copper

    Aluminum oxide coating on Iron
     
  2. jcsd
  3. when iron oxidizes, the oxidation layer keeps growing, completely consuming the object during the oxidation process. Iron rust is very porous, so oxygen can pass through the rust to reach the un-oxidized iron. Aluminium oxide for example is much more dense and very stable at room temperatures. It forms an impenetrable oxide layer and the aluminium will not oxidize further because oxygen cannot pass through the protective oxide layer. In principle you can protect iron by coating it with a thin layer of aluminium oxide.
     
  4. yes but I looked up what oxidize means and one of the definitions is to coat with an oxide.
     
  5. Borek

    Staff: Mentor

    Where have you seen this definition? I think you may be misreading your source. Coating with the oxide can be an effect of the oxidation, but it is not an oxidation itself. Oxidation is a process in which oxidation number of an element goes up. For example, metallic Al gets oxidized to Al(III) by the air oxygen and - in the process - gets covered with the oxide.
     
  6. Dictionaries like Dictionary.com say that there are 2 definition for oxidize besides loosing electrons. The first definition they have is the formation of an oxide and the second definition of it in the dictionaries is to coat with an oxide.
     
  7. Borek

    Staff: Mentor

    It is not intended to mean "cover with an oxide added as a separate substance to the surface" but "cover with an oxide produced during oxidation of the metal below".
     
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