NECE SPA CLASSES OF OXIDATIONS   Anodic oxidation is an electro-chemical process whose purpose is the creation, on the surface of aluminium frames, of a oxide coat. This coat, preserve the substrates from the action of atmospheric agents and must therefore have a thickness appropriate to the ambient for which the frames are made, and for their use.     The Norm UNI 3952/66 provides the following classes:   Thickness Use 5 For Interiors without frequent manipulation 10 For exposition to rural/urban atmosphere with periodic maintenance 15 For exposition to industrial/marine atmosphere 20 For exposition to industrial/marine atmosphere ( strengthened coat)   NECE spa suggests:   Thickness Use 5 For Interiors without frequent manipulation 10 For Interiors 15 For Externals 20 For exposition to aggressive atmosphere 25 For exposition to particularly aggressive atmosphere (British Standard BS 3987)   The Norm AAMA* 611-98 provides the following classes:   Class Thickness** Use I 18 For Exterior Apllications II 10 For Interior or Exterior Applications with regular maintenance *American Architectural Manufacturers Association. ** Minimum coating thickness in μm.