ISO/TC 79/SC 2/WG 15 - Anodic oxidation coatings on aluminium

This document specifies methods for the measurement of specular reflectance and specular gloss of flat samples of anodized aluminium using geometries of 20° (Method A), 45° (Method B), 60° (Method C) and 85° (Method D) and of specular reflectance by an additional 45° method (Method E) employing a narrow acceptance angle. The methods described are intended mainly for use with clear anodized surfaces. They can be used with colour-anodized aluminium, but only with similar colours.

This document specifies requirements for hard anodic oxidation coatings on aluminium and its alloys, including test methods. It also specifies the information to be supplied by the customer to the anodizer (see Annex A). It is not applicable to coatings produced by processes such as those referred to as plasma electrolytic oxidation, micro-arc oxidation, plasma-chemical anodic oxidation, anodic spark deposition or spark anodizing.

This document specifies a test method using electromotive force test apparatus for assessing the chemical resistance of anodic oxidation coatings on aluminium and its alloys.

This document specifies a gravimetric method for determining the mass per unit area (surface density) of anodic oxidation coatings on aluminium and its alloys. The method is applicable to all oxidation coatings formed by anodizing aluminium and its alloys, either cast or wrought, and is suitable for most aluminium alloys, except those in which the mass fraction of copper is greater than 6 %. NOTE 1 A high content of copper in the alloy can lead to increased dissolution of the substrate aluminium. NOTE 2 If the thickness is known with sufficient precision (for example, using the method specified in ISO 2128), the determination of the mass per unit area (surface density) of the coatings will enable its apparent density to be calculated. Conversely, if the conditions of application of the coating and its density are known, the determination of its mass per unit area (surface density) can permit the calculation of the average mass and an approximate evaluation of the thickness (see Clause 9).

This document specifies a method for the determination of the surface abrasion resistance of anodic oxidation coatings produced by sulfuric acid anodizing of aluminium and its alloys. It is mainly intended for the evaluation of external architectural coatings. It is a production control method that relies to a large extent on operator experience and instruction.

This document specifies an empirical method for assessing the resistance of anodic oxidation coatings to cracking by deformation. The method is applicable particularly to sheet material with anodic oxidation coatings of thickness less than 5 µm, and is useful for development purposes. NOTE If the test specimen is thick, more than 5 µm of coating can be measured (see Clause 9).

This document specifies a grid rating system that provides a means of defining levels of performance of anodic oxidation coatings on aluminium and its alloys that have been subjected to corrosion tests. This rating system is applicable to pitting corrosion resulting from — accelerated tests, — exposure to corrosive environments, and — practical service tests. This document takes into account only pitting corrosion of the basis metal resulting from penetration of the protective anodic oxidation coating. NOTE 1 ISO 8993[1] describes a similar rating system based on defined chart scales. NOTE 2 The grid rating system is frequently used for rating the results of short-term corrosion tests for relatively thin anodic oxidation coating, such as those used in the automotive industry.

This document specifies a chart rating system based on standard charts that provides a means of defining levels of performance of anodic oxidation coatings on aluminium and its alloys that have been subjected to corrosion tests. This rating system is applicable to pitting corrosion resulting from — accelerated tests, — exposure to corrosive environments, and — practical service tests. This document takes into account only pitting corrosion resulting from penetration of the protective anodic oxidation coating.

This document specifies a method for checking the continuity of thin anodic oxidation coatings on aluminium and its alloys by a copper sulfate contact test. The use of this method is limited to anodic oxidation coatings of thickness less than 5 µm or coatings that have been deformed, which includes those produced by coil anodizing techniques. NOTE The method described enables a rapid check to be made for the continuity of a thin coating of aluminium oxidation on aluminium and its alloys. In cases of doubt regarding a visible fault on the surface of a coating, the use of this method makes it possible to verify whether the fault corresponds to a local gap in the coating that exposes bare metal.

This document specifies a comparative method for the determination of the fastness of coloured anodic oxidation coatings to ultraviolet (UV) light and heat. The method is not suitable for testing coloured anodic oxidation coatings that are heat sensitive. NOTE Dark-coloured test specimens will normally reach the highest temperatures.

This document specifies the following tests: a) abrasive-wheel-wear test, determining the abrasion resistance of anodic oxidation coatings with abrasive wheel on flat specimens of aluminium and its alloys; b) abrasive jet test, determining the comparative abrasion resistance of anodic oxidation coatings with jet of abrasive particles on anodic oxidation coatings of aluminium and its alloys; c) falling sand abrasion test, determining the abrasion resistance of anodic oxidation coatings with falling sand on thin anodic oxidation coatings of aluminium and its alloys. The use of abrasive-wheel-wear test and abrasive jet test for coatings produced by hard anodizing is described in ISO 10074.

ISO 10215:2018 specifies a visual method for determining the image clarity of anodic oxidation coatings on aluminium and its alloys, using a chart scale and a lightness scale, which are defined. The method is applicable only to flat surfaces that can reflect the image of the chart scale pattern.

ISO 7599:2018 specifies a method for specifying decorative and protective anodic oxidation coatings on aluminium (including aluminium-based alloys). It defines the characteristic properties of anodic oxidation coatings, lists methods of test for checking the characteristic properties, provides minimum performance requirements, and gives information on the grades of aluminium suitable for anodizing and the importance of pretreatment to ensure the required appearance or texture of the finished work. It is not applicable to a) non-porous anodic oxidation coatings of the barrier layer type, b) anodic oxidation coatings produced by chromic acid or phosphoric acid anodizing, c) anodic oxidation coatings intended merely to prepare the substrate for subsequent application of organic coatings or for the electrodeposition of metals, and d) hard anodic oxidation coatings used mainly for engineering purposes, for which abrasion and wear resistance are the primary characteristics (see ISO 10074).

ISO 2931:2017 specifies a method for assessing the quality of sealed anodic oxidation coatings on aluminium and its alloys by measurement of the admittance. The method is applicable to anodic oxidation coatings sealed in an aqueous medium. NOTE 1 Results obtained from anodic oxidation coatings sealed by different methods, e.g. hydrothermal sealing and cold sealing, are not necessarily comparable. NOTE 2 Results obtained from anodic oxidation coatings on alloys containing more than 2 % silicon or 5 % manganese or 3 % magnesium are not comparable with results obtained from anodic oxidation coatings on more dilute alloys. The method is suitable for use as a production-control test and as an acceptance test where there is agreement between the anodizer and the customer. Any type of anodized component can be tested by the method described, provided that there is a sufficient area (a circle of diameter about 20 mm) and that the film thickness is greater than 3 µm.

ISO 2143 specifies a method of estimating the loss of absorptive power of anodic oxidation coatings that have undergone a sealing treatment, by dye absorption after acid pretreatment. The method is suitable for use as a production control method and can be applicable to anodic oxidation coatings which may be subjected to weathering or aggressive environments, or where resistance to staining is important. The method is not applicable to those coatings that a) are formed on alloys containing more than 2 % copper or 4 % silicon, b) are sealed by the dichromate process, c) have been given supplementary processing, e.g. oiling, waxing or lacquering, d) are coloured in deep shades, and e) are less than 3 μm thickness. The method is less appropriate where nickel or cobalt salts, or organic additives, have been added to baths used for hydrothermal sealing.

ISO 2135 specifies an accelerated test method for assessing the fastness, using artificial light, of coloured anodic oxidation coatings on aluminium and its alloys. For evaluating light fastness on exterior exposure, only outdoor exposure under conditions comparable with actual service is completely satisfactory. Accelerated testing is suitable as a quality-control test of coloured anodic oxidation coatings whose light fastness number has already been established by means of outdoor exposure testing. The method is applicable to coloured anodic oxidation coatings on aluminium and its alloys produced by any means and for any purpose. However, the method is not suitable for the measurement of coloured coatings with a light fastness number already established by means of outdoor exposure testing and of less than 6.

ISO 7583:2013 defines terms concerning anodized aluminium.

ISO 6719:2010 specifies a method of measuring the total and diffuse luminous reflectance characteristics of aluminium surfaces, using integrating-sphere instruments. The method specifed is also applicable to the measurement of specular reflectance (principal gloss value), specularity and diffuseness. The method is unsuitable for use with lighting reflectors.

ISO 7668:2018 specifies methods for the measurement of specular reflectance and specular gloss of flat samples of anodized aluminium using geometries of 20° (Method A), 45° (Method B), 60° (Method C) and 85° (Method D); and of specular reflectance by an additional 45° method (Method E) employing a narrow acceptance angle. The methods described are intended mainly for use with clear anodized surfaces. They can be used with colour-anodized aluminium, but only with similar colours.

ISO 10074:2017 specifies requirements for hard anodic oxidation coatings on aluminium and its alloys, including test methods. It also specifies the information to be supplied by the customer to the anodizer (see Annex A). It is not applicable to coatings produced by processes such as those referred to as plasma electrolytic oxidation, micro-arc oxidation, plasma-chemical anodic oxidation, anodic spark deposition or spark anodizing.

ISO 2106:2011 specifies a gravimetric method for determining the mass per unit area (surface density) of anodic oxidation coatings on aluminium and its alloys. The method is applicable to all oxidation coatings formed by anodizing aluminium and its alloys, either cast or wrought, and is suitable for most aluminium alloys, except those in which the copper content is greater than 6 %.

ISO 8994:2011 specifies a grid rating system that provides a means of defining levels of performance of anodic oxidation coatings on aluminium and its alloys that have been subjected to corrosion tests. This rating system is applicable to pitting corrosion resulting from accelerated tests, exposure to corrosive environments, and practical service tests. ISO 8994:2011 takes into account only pitting corrosion of the basis metal resulting from penetration of the protective anodic oxidation coating.

ISO 8251:2011 specifies the following three test methods: a) abrasive-wheel-wear test method, determining the wear resistance and the wear index of anodic oxidation coatings on flat specimens of aluminium and its alloys; b) abrasive jet test method, comparing the resistance to abrasion of anodic oxidation coatings on aluminium and its alloys with that of a standard specimen or, alternatively, a reference specimen, by use of a jet of abrasive particles; c) falling sand abrasion method, determining the abrasion resistance with falling sand applied to thin anodic oxidation coatings. The use of these methods for coatings produced by hard anodizing is described in ISO 10074.

ISO 7668:2010 specifies methods for the measurement of specular reflectance and specular gloss of flat samples of anodized aluminium using geometries of 20° (Method A), 45° (Method B), 60° (Method C) and 85° (Method D); and of specular reflectance by an additional 45° method (Method E) employing a narrow acceptance angle. The methods described are intended mainly for use with clear anodized surfaces. They can be used with colour-anodized aluminium, but only with similar colours.

ISO 7599:2010 lays down a method for specifying decorative and protective anodic oxidation coatings on aluminium (including aluminium-based alloys). It defines the characteristic properties of anodic oxidation coatings, lists methods of test for checking the characteristic properties, provides minimum performance requirements, and gives information on the grades of aluminium suitable for anodizing and the importance of pretreatment to ensure the required appearance or texture of the finished work. It is not applicable to non-porous oxidation coatings of the barrier layer type, oxidation coatings produced by chromic acid or phosphoric acid anodizing, oxidation coatings intended merely to prepare the substrate for subsequent application of organic coatings or electrodeposition of metals, or hard anodic oxidation coatings used mainly for engineering purposes, for which abrasion and wear resistance are the primary characteristics (see ISO 10074).

ISO 10074:2010 specifies requirements for hard anodic oxidation coatings on aluminium and its alloys, including test methods.

ISO 2135:2010 specifies an accelerated test method for assessing the fastness, using artificial light, of coloured anodic oxidation coatings on aluminium and its alloys. For evaluating light fastness on exterior exposure, only outdoor exposure under conditions comparable to actual service is completely satisfactory. Accelerated testing is suitable as a quality-control test of coloured anodic oxidation coatings whose light-fastness number has already been established by means of outdoor exposure testing. The method is applicable to coloured anodic oxidation coatings on aluminium and its alloys produced by any means and for any purpose. However, the method is not suitable for the measurement of coloured coatings with a light-fastness number already established by means of outdoor exposure testing, and of less than 6.

Defines levels of performance of anodic oxide coatings that have been subjected to corrosion tests. The rating system is applicable to pitting corrosion of the basis metal resulting from accelerated tests, exposure to corrosive environments and practical service tests. It is frequently used for rating the results of short term corrosion tests on relatively thin anodic coatings such as those used in the automotive industry.

The wear resistance or the wear index of the layers of oxide near the surface, of the whole oxidation coating thickness or of any selected intermediate zone may be determined. The method is applicable to all anodic oxidation coatings of thickness not less 5 micrometres on flat aluminium specimens. It is not applicable to concave or convex specimens.

ISO 7668 constitutes a revision in parts of ISO 2767:1973. The measurement is intended mainly for use with clear anodized surfaces. It can be used with colour-anodized aluminium, but then only for similar colours.

ISO 6719 specifies a method of measuring the total and diffuse luminous reflectance at different angles of incidence. The method is equally applicable to the measurement of specular reflectance (principal gloss value), specularity, and diffuseness.

The method is applicable to all oxide coatings formed by anodizing aluminium and its alloys, either cast or wrought. This method is suitable for most aluminium alloys except those in which the copper content is greater than 6 %.