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Surface Finishing Tutorial

#101 Combined Filming of Anodic Oxide and Organic Films of AL and Al Alloy - 1

Category : Anodic Oxidation Process
November 4, 2011

The standards define combined coating of anodic oxided and organic films applied on expanded aluminum materials for anti-corrosive and esthetic purposes. The Combined coating are coloring paint filmings applied after the anodizing process to give improved corrosion resistance, wheatherabilty, abrasion resistance wear property.

(1) Types

Combined filming types are classified as [Table 1] based on anodize film thickness, paint thickness, paint type.

Type Anodize filming thickness (μm)*1 Paint thickness(μm)*1 Filming Example of usage purpose
A 9.0 or more 12.0 or more Clear*2 Construction material (Harsh outdoor environment)
B 9.0 or more 7.0 or more Construction material (Outdoor), Vehicle material, etc.
C 6.0 or more 7.0 or more Construction material (Indoor), Electrical appliances, etc.
P 6.0 or more 15.0 or more Colored*3 Construction material (Outdoor), Vehicle material, etc.
  • *1 Both anodize filming and paint filming are to be of the minimum thicknesses.
  • *2 The clear filmings are meant to retain the original feel of the base materials with controlled amount of sheen.
  • *3 The colored filmings are formulated with resin based paints with pigments intended to add colors.

(2) Filming performances

Combined filmings performances are shown in [Table 2]

[Table 2] Combined filming performances
Type Anodize film performances Paint film performances
CASS corrosion resistance Adhesion Pencil scratch resistance CASS corrosion resistance Alkaline resistance Accelerated weathering resistance
Testing time (h) Rating Number (RN) Testing time (h) Rating Number (RN) Testing time (h) Rating Number (RN) Gloss retention % Discoloration
A 8 9 or more 100 / 100 H or more 48 9.5 or more 28 9.5 or more 85 or more No significant changes are to be seen
B 8 24 16
C 4 16 8 75 or more
P 4 48 24 Color differential *1
  • *1 Color differential ΔE*ab 3 or less

(3) Filming thickness test

Performed as follows with a eddy current thickness gage.

  1. Pre-measured anodize film thickness is subtracted from the total coat thickness and the paint film thickness is determined.
  2. The sum of the anodize film and the paint film is measured, then the paint film is removed with a solvent not evasive to the anodize film. The differential of the two determines the paint thickness.

(4) Paint film adhesion test

Using a cutter blade, 11 lines at 1mm interval reaching the depth of the anodize film. An adhesive tape is placed on the lines, then peeled upwards. It will be deemed 100/100 if the paint film does not peel off.

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