BS EN ISO 8289‑1:2020 pdf – Vitreous and porcelain enamels – Low-voltage test for detecting and locating defects Part 1: Swab test for non-profiled surfaces.
1 Scope This document specifies two low voltage tests for detecting and locating defects that extend to the basis metal in vitreous and porcelain enamel coatings. Method A (electrical) is applicable to the rapid detection and determination of the general location of defects. Method B (optical), based on colour effects, is applicable to the more precise detection of defects and their exact locations. Both methods are commonly applied to flat surfaces. For more intricate shapes, such as undulated and/or corrugated surfaces, ISO 8289‑2 is applicable. NOTE 1 Selection of the correct test method is critical to distinguish the areas of increased conductivity detected by method B from actual pores that extend to the basis metal, which can be detected by both methods. NOTE 2 The low voltage test is a non-destructive method of detecting defects and, therefore, is completely different from the high voltage test specified in ISO 2746. The results of the high and low voltage tests are not comparable and will differ. 2 Normative references There are no normative references in this document. 3? Terms? and? definitions For the purposes of this document, the following terms and definitions 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/ 3.1 defect pore, crack or spall that penetrates or extends to the basis metal Note 1 to entry: In certain areas, defects can be unavoidable, being caused during the production of the article, e.g. burnishing tool marks. 4 Principle Defects are detected by an electrical or electroacoustical method (method A) or an optical one (method B) based on colour effects. Testing is carried out at a low voltage, contact being made with the defect by means of a conductive solution.
The test specimen shall be cleaned with a detergent solution, rinsed with tap water and dried by dabbing with a sheet of cloth or paper. When the specimen is tested within 24 h of firing, cleaning with detergent solution is not necessary. The enamel coating shall have a temperature not greater than 30 °C. 8 Procedure 8.1 Electrical detection (method A) Mark the area to be tested by using a felt tip marker or adhesive tape. Connect the basis metal of the test specimen to the negative pole of the power source (6.1.1). Then, connect the test electrode, the sponge (6.1.2), with the positive pole of the power source (6.1.1). Soak the test electrode with the test reagent (see Clause 5). Check the electrical connection between the apparatus of 6.1.1, 6.1.2 and 6.1.3 by touching the basis metal with the test electrode. The connection is correct if the measuring instrument (6.1.3) gives an indication. Progressively scan the total enamelled test area while moving the test electrode at a speed not greater than 0,2 m/s. Count the number of electrical signals and locate the defects. 8.2 Optical detection (method B) Mark the test area by using a felt tip marker or adhesive tape. Connect the basis metal of the test specimen to the negative pole of the power source (6.2.1). Then connect the test electrode, the wet paper (6.2.2), with the positive pole of the power source (6.2.1). Soak the test electrode (6.2.2) with the test reagent (see Clause 5) and apply it, without air inclusions, to the test area. Switch on the power source (6.2.1) and switch it of after 2 min. Within 1 min of switching it off, count the number of defects. Each defect will be indicated by a red coloured spot visible on the test electrode (6.2.2).
10 Test report The test report shall contain the following information: a) reference to this document, i.e. ISO 8289-1; b) the test method used, i.e. method A or method B; c) the identification of the article tested; d) the number of defects per square metre; e) if applicable, a record of the location of the defects;