ISO 10074 Anodization of Aluminium and its Alloys - Specification for Hard Anodic Oxidation Coatings on Aluminium and its Alloys

The standard "ISO 10074 Anodization of aluminium and its alloys - Specification for hard anodic oxidation coatings on aluminium and its alloys" developed by the International Organization for Standardization (ISO) describes the requirements, including test methods, for hard anodic oxidation coatings on aluminium and its alloys. In addition, the standard annex contains the information that must be provided to the anodizer by the customer (Annex A).

It does not apply to coatings produced by processes called plasma electrolytic oxidation, micro-arc oxidation, plasma-chemical anodic oxidation, anodic spark deposition or spark anodization.

For the purposes of this standard, in addition to the terms and definitions explained in ISO 7583, the following definitions apply:

A lot refers to products that have the same nominal composition and consistency and are processed together.
Lot acceptance testing refers to testing performed on a production lot to determine its conformity to specified requirements.

The properties and characteristics of hard anodic oxidation coatings are significantly affected by both the alloy and the production method. Consequently, for the purposes of this standard, materials are classified into five alloy groups as follows:

Class 1: All wrought alloys except those in Class 2.
Class 2(a): 2000 series alloys and other alloys containing more than 5 percent copper.
Class 2(b): 2 series alloys and 5000 series alloys containing 7000 percent or more magnesium.
Class 3(a): Casting alloys containing less than 2 percent copper and/or 8 percent silicon.
Class 3(b): Other casting alloys.

The information to be provided by the customer to the anodizer must comply with the standard annex (Annex A).

The visually important surface must be completely anodized. The visual appearance must be essentially smooth. There must be no flaking, bubbling or powdery (burnt) areas. Visual inspection is based on a number of acceptance tests. Cracks or microcracks are not normally a cause for rejection.

Thickness measurements shall be made on critical surfaces, not within 5 mm of jigging marks or in the immediate vicinity of a sharp edge. Measurement shall be made using the non-destructive eddy current method described in ISO 2360 or the destructive microscopic method described in ISO 1463. In case of disagreement, the microscopic method shall be used. Measurement of thickness or, where relevant, final dimensions shall be taken in a batch acceptance test.

The surface density (mass of coating per unit area), measured in accordance with the ISO 2106 standard, shall have the minimum values in the table given in the standard on unsealed anodic oxidation coatings with a nominal thickness of 50 μm plus/minus 5 μm. If the coating thickness is not 50 μm, the surface density shall be corrected proportionally. A method specified in the ISO 2106 standard requires the use of a reagent containing chromium(VI). Chromium(VI) is toxic and its solutions are hazardous to the environment and are seriously hazardous to water.

Wear resistance should be measured on unsealed anodic oxidation coatings. Because of the good correlation with other properties, wear resistance should be tested using the abrasive wheel wear test method described in ISO 8251.

Wear resistance can be measured on sealed anodic oxidation coatings, but hydrothermal sealing or painting can reduce wear resistance by more than 50 percent.

When the abrasive wheel wear test method is not suitable (especially on some curved surfaces), resistance to wear should be tested using the abrasive jet test method described in ISO 8251. This test gives an average for the total coating thickness.

The abrasive wheel wear test method evaluates resistance to abrasion. The abrasive jet test method evaluates resistance to abrasion (erosion). Therefore, the results are not necessarily comparable.

Resistance to wear shall be determined by measuring the loss in coating thickness or the loss in coating mass. It shall be the average of at least three tests using the abrasive wheel test method described in ISO 8251. The loss in coating thickness or coating mass shall exclude any loss due to pre-test abrasion.

Acceptance values shall be in accordance with the table given in the standard. A standard sample conforming to this standard shall be tested daily under the same conditions as those used for the test sample. When loss in coating thickness is used, each thickness value shall be the average of 10 readings in the test area. The interval between the hard anodizing and the wear test shall be at least 24 hours. During this period, the test samples shall be stored in the test environment.

In the abrasive jet test method, the resistance to abrasion is determined by the mass of silicon carbide or the time required to penetrate the coating. When determined using the abrasive jet test method described in the ISO 8251 standard, the final value shall be the average of at least three tests. Acceptance values shall be in accordance with the table given in the standard. The interval between the hard anodizing and abrasion test shall be at least 24 hours. During this period, the test samples shall be stored in the test environment.

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