preface
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This document was prepared by Technical Committee ISO/TC 79, Light Metals and their Alloys, Subcommittee SC 2, Organic and anodized Coatings on Aluminium.

The fourth edition cancelled and replaced the technically revised third edition (ISO 10074:2017). The main changes from the previous edition are as follows:

– The pre-test wear test number has been added to the grinding wheel wear test as a requirement.

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ISO 10074-2021 Specification for hard anodized Coatings on aluminium and its alloys

introduce
Hard anodizing is an electrolytic treatment that forms a hard, often thick coating of alumina, used primarily for engineering purposes.

Hard anodizing can be applied to cast or forged aluminum and aluminum alloys; However, alloys and die-cast alloys containing more than 5% copper and/or 8% silicon require special anodizing procedures. In order to obtain better microhardness, wear resistance or low surface roughness characteristics, select low content alloys.

Articles shall be anodized after all heat treatment, machining, welding, molding and punching operations, unless otherwise stated. Better results on machined surfaces. Sharp edges are machined to a radius of at least 10 times the intended thickness to avoid “burning” and/or flaking.

Hard anodizing usually results in an increase in the size of each surface, equivalent to about 50% of the coating thickness. If necessary, the size of the assembly before anodizing will allow this to be done.

The thickness is usually in the range of 25μm to 150μm. Low thickness (up to 25μm) is sometimes used in a variety of applications, such as splines and threads. Normal thickness (50 μm to 80 μm) for wear or insulation requirements. High thickness (150μm) is used for repair purposes, but thick coatings tend to be softer in the outer areas. Very hard coatings reduce fatigue strength. This phenomenon can be minimized by reducing thickness and/or sealing by performing shot peening prior to hard anodizing (see H.6). Hard anodizing tends to increase surface roughness. This can be limited by low alloy content and/or mechanical finishing.

Hard anodized coatings are mainly used to obtain the following:

— wear resistance or erosion;

— electrical insulation;

– Heat insulation;

– stacking (repairing parts that exceed machining tolerances or wear parts);

— Corrosion resistance (when sealed).

1 range
This document specifies requirements for hard anodized coatings on aluminium and its alloys, including test methods.

It also specifies the information to be provided by the customer to the anodizer (see Annex A).

It is not suitable for coatings produced by plasma electrolytic oxidation, micro-arc oxidation, plasma chemical anodizing, anode spark deposition or spark anodizing processes.

ISO 10074-2021 Specification for hard anodized Coatings on aluminium and its alloys

2 Normative references
The following files are referenced in the text in such a way that some or all of the content constitutes the requirements of this document. For dated references, citation-only versions apply. For undated references, the new version of the reference (including any revisions) applies.

ISO 1463, metallic and oxide coatings – Measurement of coating thickness – Microscopic method

ISO 2106, anodizing of aluminium and its alloys — Determination of mass per unit area (surface density) of anodized coatings — Gravimetric method

ISO 2360, Non-conductive coatings on non-magnetically conductive base metals – Measurement of coating thickness – amplitude sensitive eddy current method

ISO 2376, anodizing of aluminium and its alloys — determination of breakdown voltage and voltage resistance

ISO 4516, Metallic and other inorganic coatings — Vickers and Knower microhardness tests

ISO 6344-1, coated abrasives – Particle size analysis – Part 1: particle size distribution test

ISO 7583, anodizing of aluminium and its alloys – Terms and definitions

ISO 8251, Anodizing of aluminium and its alloys – Measurement of the wear resistance of anodized coatings

ISO 9227, Corrosion testing in artificial atmospheres – salt spray testing

3 Terms and Definitions
For the purposes of this document, the terms and definitions given in ISO 7583 and the following articles apply.

3.1 A Lot

Work together on items of the same nominal composition and temper

3.2 Batch acceptance test

Test production lot (3.1) to determine compliance with specified requirements

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