इंटरनेट मानक Disclosure to Promote the Right To Information Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public. “जान1 का अ+धकार, जी1 का अ+धकार” “प0रा1 को छोड न’ 5 तरफ” Mazdoor Kisan Shakti Sangathan Jawaharlal Nehru “The Right to Information, The Right to Live” “Step Out From the Old to the New” IS 8516 (2011): ELECTRICAL INSULATING MATERIALS — DETERMINATION OF ELECTROLYTIC CORROSION CAUSED BY INSULATING MATERIALS — TEST METHODS [ETD 2: Solid Electrical Insulating Materials and Insulation Systems] “!ान $ एक न’ भारत का +नम-ण” Satyanarayan Gangaram Pitroda ““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee”” “!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै” Bhartṛhari—Nītiśatakam “Knowledge is such a treasure which cannot be stolen” IS 8516 : 2011 IEC 60426 : 2007 Hkkjrh; ekud fo|qr m"ekjks/kh lkexzh m"ekjks/kh lkexzh ls mRiUu fo|qr — vi?kV; la{kkjk Kkr djuk ijh{k.k i)fr;k¡ — ¼ igyk iqujh{k.k ½ Indian Standard ELECTRICAL INSULATING MATERIALS — DETERMINATION OF ELECTROLYTIC CORROSION CAUSED BY INSULATING MATERIALS — TEST METHODS ( First Revision ) ICS 17.220.99; 29.035.01 © BIS 2011 BU R E AU O F I N D I A N S TA N DA R D S MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002 August 2011 Price Group 8 Solid Electrical Insulating Materials and Insulating Systems Sectional Committee, ETD 02 NATIONAL FOREWORD This Indian Standard (First Revision) which is identical with IEC 60426 : 2007 ‘Electrical insulating materials — Determination of electrolytic corrosion caused by insulating materials — Test methods’ issued by the International Electrotechnical Commission (IEC) was adopted by the Bureau of Indian Standards on the recommendation of the Solid Electrical Insulating Materials and Insulating Systems Sectional Committee and approval of the Electrotechnical Division Council. This standard was first published in 1977. This revision has been undertaken to align it with the latest version of IEC 60426. The text of IEC Standard has been approved as suitable for publication as an Indian Standard without deviations. Certain terminology and conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following: a) Wherever the words ‘International Standard’ appear referring to this standard, they should be read as ‘Indian Standard’. b) Comma (,) has been used as a decimal marker while in Indian Standards, the current practice is to use a point (.) as the decimal marker. In this adopted standard, reference appears to certain International Standards for which Indian Standards also exist. The corresponding Indian Standards, which are to be substituted in their respective places are listed below along with their degree of equivalence for the editions indicated: International Standard Corresponding Indian Standard Degree of Equivalence IEC 60068-3-4 : 2001 Environmental IS 9001 (Part 4) : 1979 Guidance for Technically Equivalent testing — Part 3-4: Supporting environmental testing: Part 4 Damp documentation and guidance — Damp heat tests heat tests IEC 60454-2 Pressure-sensitive IS 7809 (Part 2) : 1977 Specification do adhesive tapes for electrical purposes for pressure sensitive adhesive tapes — Part 2: Methods of test for electrical purposes: Part 2 Methods of test For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated expressing the result of a test, shall be rounded off in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values (revised)’. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard. IS 8516 : 2011 IEC 60426 : 2007 Indian Standard ELECTRICAL INSULATING MATERIALS — DETERMINATION OF ELECTROLYTIC CORROSION CAUSED BY INSULATING MATERIALS — TEST METHODS ( First Revision ) 1 Scope This standard determines the ability of insulating materials to produce electrolytic corrosion on metals being in contact with them under the influence of electric stress, high humidity and elevated temperature. The effect of electrolytic corrosion is assessed in one test by using consecutively two methods: • visual semi-quantitative method consisting in comparing visually the corrosion appearing on the anode and cathode metal strips, with those given in the reference figures. This method consists of the direct visual assessment of the degree of corrosion of two copper strips, acting as anode and cathode respectively, placed in contact with the tested insulating material under a d.c. potential difference at specified environmental conditions. The degree of corrosion is assessed by visually comparing the corrosion marks on the anode and cathode metal strips with those shown in the reference figures; • quantitative method, which involves the tensile strength measurement, carried out on the same anode and cathode metal strips after visual inspection. An additional quantitative test method for determining electrolytic corrosion, which involves tensile strength measurement of copper wire, is described in the informative Annex C. 2 Normative references The following referenced documents are indispensable for the application 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. IEC 60068-3-4:2001, Environmental testing – Part 3-4: Supporting documentation and guidance – Damp heat tests IEC 60454-2:⎯, Pressure-sensitive adhesive tapes for electrical purposes – Part 2: Methods of test1 3 Terms and definitions For the purposes of this document the following terms and definitions apply: 3.1 electrolytic corrosion kind of galvanic corrosion caused by joint action of external source of d.c. potential and some substances included in some organic materials in presence of high humidity and elevated temperature ————————— 1 To be published 1 IS 8516 : 2011 IEC 60426 : 2007 3.2 test strip a) positive a metal strip connected with positive pole of direct current source which forms the anode in the contact system: metal – insulating material b) negative a metal strip connected with negative pole of direct current source which forms the cathode in the contact system: metal – insulating material 3.3 surface of contact a) of tested material part of insulating material specimen which is in direct contact with metal strips b) of metal strip part of metal strip (positive or negative) which is in direct contact with insulating material specimen 4 General description of the test method The test consists of applying specified environmental conditions and a d.c. potential difference to two parallel copper strips 3 mm apart, acting as the anode and the cathode respectively. The insulating material under test (test specimen) is placed across these two strips. In order to obtain a good and uniform contact between the metal strips and the material under test, the test specimen is pressed to the strips by a cylindrical loading tube. 5 Test specimens 5.1 General The preparation of the specimens depends on the type of material and the form in which it is supplied. The shape and dimensions of the test specimen are shown in Figure 1. Procedures for the preparation of the test specimen are reported beneath (5.2 to 5.7). Dimensions in millimetres Surface of contact 4,0 ± 0,1 5 0, ± 0 0, 1 40 ± 1 IEC 122/07 Figure 1 – Test specimen of rigid material, for example textile laminate 2 IS 8516 : 2011 IEC 60426 : 2007 5.2 Cut surfaces of rigid materials (blocks, plates, sheets or semi-finished materials) The test specimens shall be cut out or machined from the tested material to a thickness of 4 mm, by means of a dry method without the use of cutting oils or lubricants and without overheating or damaging them. It is recommended to take several test specimens from various layers of the product. It is permissible to use the test specimens of thickness smaller than 4 mm, but not smaller than 2 mm. The contact surface of the test specimen shall be smoothed using abrasive paper. Care should be taken to keep parallelism of the opposite surfaces of the test specimen, in order to assure a good contact of the test specimen to the metal strips. The surface of contact should not show any flaws, cracks, inclusions or bubbles. The abrasive paper shall not contain any contaminations causing a bad corrosion index, for example halogen components. 5.3 Cast, moulding, injection and pressed materials From insulating materials delivered in the form of liquid resin, moulding powder or granules, the test specimens shall be made in shapes and dimensions as shown in Figure 1. The specimens shall be made by casting or pressing in a special mould, following exactly the technological instruction recommended by the manufacturer of the tested material. The test specimen and surface of contact shall be prepared as given in 5.2. 5.4 Cut surfaces of flexible films, foils and thin sheets Test specimens of these products shall be made up in layers to form small packs placed between suitable holding plates of insulating material not causing electrolytic corrosion itself, for example polymethylmethacrylate (Plexiglas® 2). The preferred thickness of holding plates is 1 mm ± 0,2 mm. The thickness of a pack should be approximately of 4 mm or 2 mm, depending on the thickness of the tested foils. The value of 4 mm is recommended in the case of the single foil thickness being less than 2 mm and more than 0,5 mm, whereas that one of 2 mm is recommended if the single foil thickness is less than 0,5 mm. These test blocks shall be compressed with screws made of the same material as holding plates and then machined to the appropriate shape as shown in Figure 2. The material to be tested should protrude 0,2 mm to 0,5 mm beyond the holding plates. ————————— 2 Plexiglas® is an example of a suitable product available commercially. This information is given for the convenience of users of this document and does not constitute an endorsement by IEC of this product. 3 IS 8516 : 2011 IEC 60426 : 2007 Dimensions in millimetres Holding plates Surface of contact 5 0, o 2 t 1,0 ± 0,2 0, 5 0, ± 0 2 or 4 0, 1 40 ± 1 IEC 123/07 Figure 2 – Test specimen of flexible material, for example flexible films, foils etc. Apart from this, the particulars given in 5.2 apply. 5.5 Adhesive tapes For adhesive tapes the method of Clause 7 of IEC 60454-2 is recommended. 5.6 Flexible sleeving and tubing Sleeving and tubing (both varnished fabric and extruded) are slit open, so as to make flat sheets, which can then be prepared as for films (see 5.4). 5.7 Lacquers and insulating varnishes The lacquer or insulating varnish to be tested shall be applied in the manner recommended by the manufacturer to the surface of a test specimen of shape as shown in Figure 1 and described in 5.2. The base material of the test specimen shall be a corrosion free plastic such as polymethylmethacrylate. In case of solvent incompatibility or a baking temperature being too high for the base material, another suitable base material such as cast, hot cured corrosion free epoxy resin or glass shall be used. If the lacquer or insulating varnish is designed to contribute freedom from corrosion to another material, a test specimen of that material shall be used. The tested lacquer or varnish shall be sprayed, dipped or otherwise coated to the desired thickness and baked, if necessary, as specified or according to the directions of the manufacturer. If the thickness of coating is not determined by specification or direction of the manufacturer, it shall be of (30 ± 10) μm. 5.8 Cleanliness of contact surfaces When preparing and handling the test specimens, any soiling of the test surfaces, for example by perspiration from the hands, shall be avoided. The specimens shall be touched only with a pair of tweezers or with protecting gloves made of materials free from corrosion (e.g. polyethylene). After the test specimens h ave been machined or cut, their surfaces shall be cleaned with a soft brush. Before cleaning, the brush shall be rinsed in ethanol (96 %) and then dried. 4 IS 8516 : 2011 IEC 60426 : 2007 After the cleaning procedure, the surface of contact shall not show any foreign particles, residues of oil or grease, no mould residues, etc. 5.9 Number of test specimens At least five test specimens made from the same material shall be tested at the same time. A specific sampling procedure may be desired. If necessary, such a sampling procedure should be specified and used. 6 Test strips 6.1 General The test strips shall be made of 0,1 mm thick, semi-hard copper of purity 99,9 Cu. Their dimensions are 10 mm wide and 200 mm long. The test strips shall be flat, without bends and burrs at the edges as well as any other mechanical defects or impurities on the test surface, which may have influence on the test results. NOTE Test strips of brass or aluminium can be made in the same way. 6.2 Preparation of the test strips From each new reel of strip (sold as a semi-finished product) the first several decimetres of the strip shall be rejected and then the suitable number of strip segments, each 200 mm long, shall be cut-off. Copper strips shall be degreased with a low boiling point organic solvent (e.g. acetone or hexane) and then etched. Etching shall be carried out at laboratory temperature, with a solution of the following composition: sulphuric acid (1,82) with a mass fraction of 73 %, nitric acid (1,33) with a mass fraction of 26 %, sodium chloride with a mass fraction of 0,5 % and hard carbon black with a mass fraction of 0,5 %. The time of etching shall be between 20 s to 60 s. All strips, which are destined for one set of testing, shall be etched at the same time. The coarseness of the strip surface can be controlled by adjustment of the etching time until the copper strip has an even dull sheen. The strips shall then be washed in distilled water, then dipped in ethanol and dried with blotting paper. NOTE Unevenness of the surface of the strip may influence the discolouration and may lead to a wrong evaluation. A surface, which is evenly dull, shows a discolouration of greater intensity than a surface, which is slightly corroded, semi-dull or brilliant. After degreasing and etching, both ends of the strip shall be reeled loose to the shape as shown in Figure 3. So prepared test strips shall be immediately (within 20 min) mounted in the test device, ready for the test procedure, as shown in Figure 4. 5