BS EN ISO 2376:2019 pdf – Anodizing of aluminium and its alloys – Determination of breakdown voltage and withstand voltage.
1 Scope This document specifies test methods for the determination of the breakdown voltage and withstand voltage of anodic oxidation coatings on aluminium and its alloys, on flat or near-flat surfaces and on round wire. The methods are applicable to anodic oxidation coatings used primarily as electrical insulators. The methods are not applicable to coatings in the vicinity of cut edges, the edges of holes, or sharp changes of angle on, for example, extruded shapes. NOTE 1 Breakdown voltage and withstand voltage are affected by relative humidity. NOTE 2 The methods described do not give satisfactory results for unsealed coatings because they are affected by the humidity in particular. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 7583, Anodizing of aluminium and its alloys — Terms and definitions 3? Terms? and? definitions For the purposes of this document, the terms and definitions given in ISO 7583 apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https://www.iso.org/obp — IEC Electropedia: available at http://www.electropedia.org/ 4 Principle The electric voltage at which current first passes through an anodic oxidation coating is measured. These breakdown voltage and withstand voltage are a function of the dielectric characteristics and the insulation properties of the anodic oxidation coatings. The breakdown voltage and withstand voltage depend upon the thickness of the coating, as well as on many other factors, particularly the composition of the basis metal, its surface condition, the effectiveness of sealing, the dryness of the test specimen and the degree of ageing.
5.5 Voltage-measuring device, which gives r.m.s. values, expressed in volts. 5.6 Electrode probe, made from conducting material, suitably insulated for handling purposes, free to move as required and adequately supported. The contact surface shall be spherical with a diameter of 3 mm to 8 mm and shall be maintained in a smooth, untarnished condition. The design of the probe shall be such that, when the spherical surface is placed on the surface of the anodized test specimen, the total force exerted on the coating is 0,5 N to 1,0 N (a probe of mass 50 g to 100 g is suitable). 5.7 Contact plate, for testing flat test specimens, having a smooth, bright, metallic surface, or a contact probe or clip which is capable of breaking through to the basis metal (7.1). 5.8 Twisting machine, for testing round wire, having two sets of jaws 400 mm apart, with one set of jaws fixed, while the other set is free to rotate. The jaws shall be mounted so as to prevent lateral movement of the jaws when the twisting operation is carried out (7.2). 6 Test specimen 6.1 Sampling The test specimen shall be taken from a significant surface of the product, where the anodic oxidation coating formed thereon needs to satisfy the quality adapted to the application of the product. The test specimen shall not be taken from the edges for possible distortion and/or non-uniformity. Where it is impossible to test the product itself, a test specimen which is representative of the product may be used. In this case, the test specimen used shall be made from the same material and prepared under the same conditions of finishing as those used for the preparation of the product. The aluminium alloy, the manufacturing conditions (kind and temper of the material), and the surface condition before treatment shall be the same as those of the product. Pretreatment and anodizing shall be performed in the same bath and under the same conditions as the treatment of the product.