The Collaborative International Dictionary of English v.0.48:

oxidization \oxidization\ n.
   The process of oxidizing; the addition of oxygen to a
   compound with a loss of electrons. The process always occurs
   accompanied by reduction.

   Syn: oxidation, oxidisation.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

oxidization
    n 1: the process of oxidizing; the addition of oxygen to a
         compound with a loss of electrons; always occurs
         accompanied by reduction [syn: oxidation, oxidization,
         oxidisation]