SANS 8502-2-2008 Preparation of steel substrates before application of paint and related products - Tests for the assessment of surface cleanliness Part 2 Laboratory determination .pdf

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2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any

3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-21222-3 SANS 8502-2:2008Edition 1ISO 8502-2:2005Edition 2SOUTH AFRICAN NATIONAL STANDARD Preparation of steel substrates before applicatio

4、n of paints and related products Tests for the assessment of surface cleanliness Part 2: Laboratory determination of chloride on cleaned surfaces This national standard is the identical implementation of ISO 8502-2:2005 (corrected version:2006) and is adopted with the permission of the International

5、 Organization for Standardization. Published by Standards South Africa 1 dr lategan road groenkloof private bag x191 pretoria 0001 tel: 012 428 7911 fax: 012 344 1568 international code + 27 12 www.stansa.co.za Standards South Africa SANS 8502-2:2008 Edition 1 ISO 8502-2:2005 Edition 2 Table of chan

6、ges Change No. Date Scope National foreword This South African standard was approved by National Committee StanSA SC 5140.11D, Paints and varnishes Industrial coatings, in accordance with procedures of Standards South Africa, in compliance with annex 3 of the WTO/TBT agreement. This document was pub

7、lished in April 2008. Reference numberISO 8502-2:2005(E)ISO 2005INTERNATIONAL STANDARD ISO8502-2Second edition2005-10-15Corrected version2006-01-15Preparation of steel substrates before application of paints and related products Tests for the assessment of surface cleanliness Part 2: Laboratory dete

8、rmination of chloride on cleaned surfaces Prparation des subjectiles dacier avant application de peintures et de produits assimils Essais pour apprcier la propret dune surface Partie 2: Recherche en laboratoire des chlorures sur les surfaces nettoyes SANS 8502-2:2008This s tandard may only be used a

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13、ut permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2005 All righ

14、ts reservedSANS 8502-2:2008This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .ISO 8502-2:2005(E) ISO 2005 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Principle. 2 4 Reagents and materi

15、als . 2 5 Apparatus 3 6 Procedure 3 6.1 Blank titration 3 6.2 Washing of the surface 3 6.3 Wash-water titration . 4 7 Expression of results . 4 8 Test report . 5 Bibliography . 6 SANS 8502-2:2008This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS

16、.ISO 8502-2:2005(E) iv ISO 2005 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Eac

17、h member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the Internation

18、al Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standard

19、s adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject o

20、f patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 8502-2 was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee SC 12, Preparation of steel substrates before application of paints and related products. This second edition

21、 cancels and replaces the first edition (ISO 8502-2:1992), which has been technically revised. ISO 8502 consists of the following parts, under the general title Preparation of steel substrates before application of paints and related products Tests for the assessment of surface cleanliness: Part 1:

22、Field test for soluble iron corrosion products (withdrawn) Technical Report Part 2: Laboratory determination of chloride on cleaned surfaces Part 3: Assessment of dust on steel surfaces prepared for painting (pressure-sensitive tape method) Part 4: Guidance on the estimation of the probability of co

23、ndensation prior to paint application Part 5: Measurement of chloride on steel surfaces prepared for painting (ion detection tube method) Part 6: Extraction of soluble contaminants for analysis The Bresle method Part 8: Field method for the refractometric determination of moisture Part 9: Field meth

24、od for the conductometric determination of water-soluble salts Part 10: Field method for the titrimetric determination of water-soluble chloride (withdrawn) Part 11: Field method for the turbidimetric determination of water-soluble sulfate Part 12: Field method for the titrimetric determination of w

25、ater-soluble ferrous ions This corrected version of ISO 8502-2:2005 incorporates the following corrections: in 4.5 “0,012 5 mg/l” has been changed to “0,012 5 mol/l”; in 4.5.2 the numerator in the equation has been changed from “2,8 105” to “2,8 102” and the volume unit has been added in the where c

26、lause, giving “V is the volume, in millilitres, of the mercury(II) nitrate solution consumed.” SANS 8502-2:2008This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .ISO 8502-2:2005(E) ISO 2005 All rights reserved vIntroduction The performance of pr

27、otective coatings of paint and related products applied to steel is significantly affected by the state of the steel surface immediately prior to painting. The principal factors that are known to influence this performance are a) the presence of rust and mill scale, b) the presence of surface contam

28、inants, including salts, dust, oils and greases, and c) the surface profile. ISO 8501, ISO 8502 and ISO 8503 have been prepared to provide methods of assessing these factors, while ISO 8504 provides guidance on the preparation methods that are available for cleaning steel substrates, indicating the

29、capabilities of each in attaining specified levels of cleanliness. These International Standards do not contain recommendations for the protective coating systems to be applied to the steel surface. Neither do they contain recommendations for the surface quality requirements for specific situations

30、even though surface quality can have a direct influence on the choice of protective coating to be applied and on its performance. Such recommendations are found in other documents such as national standards and codes of practice. It will be necessary for the users of these International Standards to

31、 ensure that the qualities specified are compatible and appropriate both for the environmental conditions to which the steel will be exposed and for the protective coating system to be used, and within the capability of the cleaning procedure specified. The four International Standards referred to a

32、bove deal with the following aspects of preparation of steel substrates before application of paints and related products: ISO 8501 on visual assessment of surface cleanliness; ISO 8502 on tests for the assessment of surface cleanliness; ISO 8503 on surface roughness characteristics of blast-cleaned

33、 steel substrates; ISO 8504 on surface preparation methods. Each of these International Standards is in turn divided into separate parts. This part of ISO 8502 describes a method for the assessment of chloride-containing salts that are readily soluble in water and are present on a steel surface. Rus

34、ted steel substrates, particularly of rust grades C or D (see ISO 8501-1), even when blast cleaned to preparation grade Sa 3 (see ISO 8501-1) can still be contaminated by soluble salts and corrosion products. These compounds are almost colourless and are localized at the lowest point of the rust pit

35、s. If they are not removed prior to painting, chemical reactions can result in large accumulations of rust that destroy the adhesion between the substrate and the applied protective coating. Even if the salt is readily soluble in water, it is often impossible to remove it completely from the surface

36、 by a simple washing such as that described in this procedure. The method does not therefore determine the total amount of chloride on the surface but gives an indication of the cleanliness level of the surface. Prolonging the washing time should remove a larger proportion of the salt. SANS 8502-2:2

37、008This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .SANS 8502-2:2008This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .INTERNATIONAL STANDARD ISO 8502-2:2005(E) ISO 2005 All rights reserve

38、d 1Preparation of steel substrates before application of paints and related products Tests for the assessment of surface cleanliness Part 2: Laboratory determination of chloride on cleaned surfaces WARNING The procedure described in this part of ISO 8502 is intended to be carried out by qualified ch

39、emists or by other suitably trained and/or supervised personnel. The substances and procedures used in this method may be injurious to health if adequate precautions are not taken. Attention is drawn in the text (see 4.5) to certain specific hazards. This part of ISO 8502 refers only to its technica

40、l suitability and does not absolve the user from statutory obligations relating to health and safety. 1 Scope This part of ISO 8502 describes a method for the determination of chloride-containing salts that are readily soluble in water and are present on a steel surface. The method is also applicabl

41、e to previously coated surfaces. It will normally be used in a laboratory using washings sampled from surfaces on site. The method is applicable to the determination of salts that have been deposited on the steel surface before, during or after the cleaning operations. NOTE 1 Although the procedure

42、for chloride determination is generally accurate, the overall precision of the method is limited by uncertainties in the sampling procedure. In addition, traces of iron chloride at the bottom of pits are difficult to extract into the sample. The test method is not applicable to surfaces treated with

43、 chromate, nitrite or amine, which are commonly used as inhibitors in the water when wet blast-cleaning. This is because a chromate concentration of 10 mg/l or greater or a nitrite concentration of 20 mg/l or greater in the wash water interferes with the determination of the chloride. Also the amine

44、 inhibitors can form a hydroxide boundary layer (not water soluble) over the substrate and prevent the water from contacting the underlying salt for its removal. An iron(III) ion concentration of 10 mg/l also interferes with the determination, but the iron(III) ions are concentrated in the rust depo

45、sits, which are removed from the test solution by filtration. NOTE 2 The performance of a paint system is affected by the amount of soluble chloride remaining on the surface. The acceptable level of this contamination is related to the service conditions. For further information regarding levels of

46、water-soluble salt contamination see ISO/TR 15235 1. 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 (includin

47、g any amendments) applies. ISO 3696:1987, Water for analytical laboratory use Specification and test methods SANS 8502-2:2008This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .ISO 8502-2:2005(E) 2 ISO 2005 All rights reserved3 Principle A define

48、d area of the steel surface is washed with a known volume of water and the chloride in the wash water is titrated with mercury(II) nitrate using a diphenylcarbazone/bromophenol blue mixed indicator titration method. In the titration, mercury ions react with free chloride ions to form HgCI2, which di

49、ssociates only slightly. When the chloride ions are consumed, the excess mercury ions give an intense violet colour with diphenylcarbazone, indicating the end-point of the titration. 4 Reagents and materials During the analysis, use only reagents of recognized analytical grade. 4.1 Water, conforming to the requirements of grade 3 of ISO 3696. 4.2 Nitric acid, c(HNO3) about 0,05 mol/l. Add 3,5 ml of concentrated nitric acid ( = 1,40 g/ml) to some water and make up to 1 000 ml with w