ISO 8289-1-2020 pdf free download – Vitreous and porcelain enamels – Low-voltage test for detecting and locating defects – Part 1: Swab test for non- profiled surfaces (ISO 8289-1:2020).
5Test reagent
Dissolve 3,0 g ± 0,1 g sodium nitrite (NaNO2) in 100 ml of tap water and add two drops of a liquiddishwashing detergent.
lf the defects are to be made visible by means of colour effects (method B), add 4 ml of phenolphthaleinethanolic solution having a mass fraction of 0,5 % phenolphthalein.
WARNING —Care should be taken when using the sodium nitrite and phenolphthalein solution.Instead of sodium nitrite, other water-soluble salts may be used provided that the article is not re-enamelled after testing.The salt solution shall be used in such an amount that the alternative testreagent has a conductivity of 35 mS ± 3 ms and a pH value of 7,5±1.
6 Apparatus
6.1Method A6.1.1 Power source.
The power source for method A shall consist of a 9 V battery device with an accuracy of ±1 V.Forexample, 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. Forrough scanning of large enamelled surfaces, test electrodes with an area of not greater than 100 cm2shall be used.Any defects that are detected shall then be more precisely located using a test electrodewith 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 indicateswhen the electrical restance of the vitreous enamel drops below 90 kD ± 9 kQ shall be used to detectand locate defects in the coating.
6.2Method B
6.2.1 Power source.
The power source for method B shall consist of a source of direct voltage (DC voltage),24V± 4V.Alternatively, a voltage divider, or three transistor radio batteries,6 F 100, as specified in IEC 60086-2.connected in series may be employed.
6.2.2Test electrode.
Wet paper, for example,kitchen tissue, with an area of at least 500 cm2, shall be used as the testelectrode for method B.
7Test specimen
The test specimen may be a commercial item, a part thereof or a sample plate especially preparedfor this test. In any case, the test specimen shall have an uncovered (not enamelled) area of metal for contact with the negative electrode.
The test specimen shall be cleaned with a detergent solution,rinsed with tap water and dried bydabbing with a sheet of cloth or paper. When the specimen is tested within 24 h of firing, cleaning withdetergent solution is not necessary.The enamel coating shall have a temperature not greater than 30 8C.
8Procedure
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 thetest specimen to the negative pole of the power source(6.1.1).Then, connect the test electrode, thesponge (6.1.2), with the positive pole of the power source(6.1.1). Soak the test electrode with the testreagent (see Clause 5).
Check the electrical connection between the apparatus of 6.1.1,6.1.2 and 6.1.3 by touching the basismetal with the test electrode. The connection is correct if the measuring instrument (6.1.3) givesan indication.
Progressively scan the total enamelled test area while moving the test electrode at a speed not greaterthan 0,2 m/s.Count the number of electrical signals and locate the defects.
8.2Optical detection (method B)
Mark the test area by using a felt tip marker or adhesive tape.Connect the basis metal of the testspecimen to the negative pole of the power source(6.2.1).Then connect the test electrode, the wetpaper(6.2.2), with the positive pole of the power source(6.2.1).Soak the test electrode(6.2.2) with thetest 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 of,count the number of defects. Each defect will be indicated by a red coloured spot visible on the testelectrode (6.2.2).ISO 8289-1 pdf download.