BS EN ISO 8289-1-2020 Vitreous and porcelain enamels – Low-voltage test for detecting and locating defects Part 1: Swab test for non-profiled surfaces.
5 Test reagent
Dissolve 3.0 g ± 0.1 g sodium nitrite (NaNO2) in 100 ml of tap water and add two drops of a liquid dishwashing detergent.
If the defects are to be made visible by means of colour effects (method B). add 4 ml of phenolphthalein ethanolic solution having a mass fraction of 0,5 % phenolphthalein.
WARNING — Care should be taken when using the sodium nitrite and phenolphthaleln solution.
Instead of sodium nitrite, other water-soluble salts may be used provided that the article is not reenamelled after testing. The salt solution shall be used in such an amount that the alternative test reagent has a conductivity of 35 mS ± 3 mS and a pH value of 7,5 ± 1.
6.1 Method A
6.1.1 Power source.
The power source for method A shall consist of a 9 V battery device with an accuracy of ±1 V. For example, a transistor battery, 6 F 100, as specified in IEC 60086-2. is suitable.
6.1.2 Test electrode.
The test electrode for method A consists of a sponge made of plastic, cellulose or similar material. For rough scanning of large enamelled surfaces, test electrodes with an area of not greater than 100 cm2 shall be used. Any defects that are detected shall then be more precisely located using a test electrode with an area of about 1 cm2 or by using an edge or corner of the larger electrode.
6.1.3 Measuring instrument.
A sensitive microammeter or an electronic circuit that produces an acoustical signal that indicates when the electrical restance of the vitreous enamel drops below 90 kfl ± 9 kfl shall be used to detect and locate defects in the coating.
6.2 Method B
6.2.1 Power source.
The power source for method B shall consist of a source of direct voltage (DC voltage), 24 V ± 4 V. Alternatively, a voltage divider, or three transistor radio batteries, 6 F 100, as specified in fEC 6008LiZ. con nected in series may be employed.
6.2.2 Test electrode.
Wet paper, for example, kitchen tissue, with an area ot at least 500 cm2, shall be used as the test
electrode for method B.
7 Test specimen
The test specimen may be a commercial item, a part thereof or a sample plate especially prepared for this test. In any case, the test specimen shall have an uncovered (not enamelled) area of metal for contact with the negative electrode.BS EN ISO 8289-1 pdf download.