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The Oxidation Process

The anodic oxidation of aluminum is an electrochemical process which consists in the creation of an aluminum oxide layer resistant to atmospheric corrosion on the surface of the treated material.
This process is carried out through its immersion in tanks which contain various chemical substances with different concentration values.
The treated material undergoes the following processes, according to the kind of finish required:

Acid Neutralization

  • The purpose of this process is to remove hydroxides from the surface of the treated material and to neutralize its basicity through its immersion in a tank containing a sulfuric acid solution
  • Tank used for acid neutralization
    Tank used for acid neutralization

Degreasing

  • Its purpose is to remove traces of organic substances from the treated material through its immersion in a tank containing an alkaline cleaner at high temperature.
  • Degreased material
    Degreased material

Chemical Glazing

  • The purpose of this process is to give the product, which has not been previously brushed, a satin surface conventionally defined with the acronym ARC.
    This process is carried out also on the aluminum which has undergone a shorter mechanical cleaning, with the purpose of rendering its surface more homogenous.
    The treated material is immersed in a tank containing a solution of Caustic Soda at high temperature.
  • The process of chemical glazing
    The process of chemical glazing

Sulfuric Acid Anodizing

  • It is an electrochemical process that modifies the aluminum surface to form an oxide layer, which varies in thickness, through its immersion in tanks containing a sulfuric acid solution. The treated material is connected to the positive electrode (anode) of a constant current generator.
    This process may last from 15 to 60 minutes, according to the thickness required, which is measured in microns. Aluminum oxide is hard, compact, it can be dyed and it is resistant to atmospheric corrosion.
  • Tank for sulfuric acid anodizing
    Tank for sulfuric acid anodizing

Alkaline Neutralization

  • The immersion of the treated material in this tank, which contains sodium carbonate, has the purpose of removing traces of sulfuric acid from its pores.

Inorganic Dyeing

  • This process, which is used to dye the treated material, is based on the precipitation of metallic compounds into the pores of the oxide surface through its immersion in tanks containing Cobalt Acetate and Potassium Permanganate (bronze and dark brown colours) or Ferric Ammonium Oxalate (golden colour) at given concentration and pH values.
  • The process of inorganic dyeing
    The process of inorganic dyeing

Electrolytic Dieying

  • In this dyeing process, the treated material is subject to pulsed current in a tank containing a solution of metallic salts and other chemical additives.
  • Tank used for electrolytic dyeing
    Tank used for electrolytic dyeing

Sealing

  • In this process, the pores of the anodic oxide are sealed, generally through the conversion of the oxide into its hydrated form at high temperature. The treated material is immersed for a certain period of time in a tank containing a solution of water and additives at a temperature of about 100° C (Hot sealing).
  • The process of sealing
    The process of sealing

Washing

  • The treated material is repeatedly washed during the whole process through its immersion in tanks containing running and/or static water.