1、BS EN ISO21227-4:2008ICS 87.040NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDPaints and varnishes Evaluation of defectson coated surfacesusing optical imagingPart 4: Evaluation of filiform corrosion(ISO 21227-4:2008)This British Standardwas published under the
2、authority of the StandardsPolicy and StrategyCommittee on 31 July 2008 BSI 2008ISBN 978 0 580 62647 0Amendments/corrigenda issued since publicationDate CommentsBS EN ISO 21227-4:2008National forewordThis British Standard is the UK implementation of EN ISO21227-4:2008.The UK participation in its prep
3、aration was entrusted to TechnicalCommittee STI/10, Test methods for paints.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct a
4、pplication.Compliance with a British Standard cannot confer immunityfrom legal obligations.EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 21227-4March 2008ICS 87.040English VersionPaints and varnishes - Evaluation of defects on coated surfacesusing optical imaging - Part 4: Evaluation of fili
5、form corrosion(ISO 21227-4:2008)Peintures et vernis - valuation par imagerie optique desdfauts des surfaces revtues - Partie 4: valuation de lacorrosion filiforme (ISO 21227-4:2008)Beschichtungsstoffe - Beurteilung vonBeschichtungsschden mittels digitaler Bildverarbeitung -Teil 4: Beurteilung von Fi
6、liformkorrosion (ISO 21227-4:2008)This European Standard was approved by CEN on 21 February 2008.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-d
7、ate lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the
8、 responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary,
9、 Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de
10、 Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 21227-4:2008: EBS EN ISO 21227-4:2008EN ISO 21227-4:2008 (E) 3 Foreword This document (EN ISO 21227-4:2008) has been prepared by Technical Committ
11、ee ISO/TC 35 “Paints and varnishes“ in collaboration with Technical Committee CEN/TC 139 “Paints and varnishes” the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the lates
12、t by September 2008, and conflicting national standards shall be withdrawn at the latest by September 2008. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or al
13、l such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ice
14、land, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 21227-4:2008 has been approved by CEN as a EN ISO 21227-4:2008 without any modificatio
15、n. BS EN ISO 21227-4:2008ISO 21227-4:2008(E) ISO 2008 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 1 4 Principle. 2 5 Requirements 2 6 Calibration . 2 7 Procedure 2 8 Image evaluation. 3 9 Precision 4 10 Test report .
16、 4 Annex A (informative) Extended evaluation 6 Bibliography . 7 BS EN ISO 21227-4:2008ISO 21227-4:2008(E) iv ISO 2008 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing
17、 International Standards is normally carried out through ISO technical committees. Each 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 liais
18、on with ISO, also take part in the work. ISO collaborates closely with the International 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 te
19、chnical committees is to prepare International Standards. Draft International Standards 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 dr
20、awn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 21227-4 was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee SC 9, General test met
21、hods for paints and varnishes, in collaboration with Technical Committee CEN/TC 139, Paints and varnishes. ISO 21227 consists of the following parts, under the general title Paints and varnishes Evaluation of defects on coated surfaces using optical imaging: Part 1: General guidance Part 2: Evaluati
22、on procedure for multi-impact stone-chipping test Part 3: Evaluation of delamination and corrosion around a scribe Part 4: Evaluation of filiform corrosion BS EN ISO 21227-4:2008ISO 21227-4:2008(E) ISO 2008 All rights reserved vIntroduction Conventional ISO test methods used for evaluating surface d
23、efects and appearance changes often utilize pictorial standards which depict particular types of surface deterioration and require human visual evaluation. The technology described in the various parts of this International Standard can yield more objective, accurate, quantitative and reproducible r
24、esults when compared to the human visual evaluation techniques. BS EN ISO 21227-4:2008BS EN ISO 21227-4:2008INTERNATIONAL STANDARD ISO 21227-4:2008(E) ISO 2008 All rights reserved 1Paints and varnishes Evaluation of defects on coated surfaces using optical imaging Part 4: Evaluation of filiform corr
25、osion 1 Scope This part of ISO 21227 describes a method for evaluating filiform corrosion by means of digital optical imaging. The filiform corrosion can be produced in accordance with ISO 4623-1, ISO 4623-2 or EN 3665. 2 Normative references The following referenced documents are indispensable for
26、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. ISO 4623-1, Paints and varnishes Determination of resistance to filiform corrosion Part 1: Steel substrate
27、s ISO 4623-2, Paints and varnishes Determination of resistance to filiform corrosion Part 2: Aluminium substrates ISO 21227-1, Paints and varnishes Evaluation of defects on coated surfaces using optical imaging Part 1: General guidance EN 3665, Aerospace series Test methods for paints and varnishes
28、Filiform corrosion resistance test on aluminium alloys 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 21227-1 and the following apply. 3.1 filiform corrosion type of corrosion proceeding under a coat of paint, varnish or related product, in the form
29、 of filaments, generally starting from bare edges or from local damage to the coating NOTE 1 Usually, the filaments are irregular in length and direction of growth, but they may also be nearly parallel and of approximately equal length. NOTE 2 Filiform corrosion can also occur under other protective
30、 coatings. ISO 4623-1 BS EN ISO 21227-4:2008ISO 21227-4:2008(E) 2 ISO 2008 All rights reserved4 Principle A grey-scale or colour image is produced from the original image of the surface showing filiform corrosion. In the simplest case, this image is converted into a binary image (thresholding). The
31、damaged area and the maximum filament length are measured, and the mean width of the filiform corrosion is calculated. 5 Requirements 5.1 General The requirements laid down in ISO 21227-1 also apply for this part of ISO 21227. 5.2 Illumination The illumination shall be such that the damaged area can
32、 be clearly distinguished from the undamaged area. Bright-field or dark-field illumination can be used. NOTE 1 In the case of glossy specimens, directional illumination is suitable. For matt specimens, dark-field illumination is recommended. NOTE 2 When detecting filiform corrosion without previousl
33、y removing the coating, directional reflection illumination can be of advantage because of the low contrast. After stripping the coating, filiform corrosion can be readily recognized when using diffuse reflection illumination, provided the contrast is sufficiently high. 5.3 Resolution The minimum re
34、solution shall be 6 pixels per millimetre. NOTE Different resolutions, in particular in the case of damage involving a large number of filaments, can lead to different values for the damaged area. 6 Calibration By calibrating the scale in both the x and y directions (e.g. with an object micrometer o
35、r a photographic picture graduated in millimetres), the digitized image can be measured with sufficient accuracy. 7 Procedure Prepare the test panels in accordance with ISO 4623-1, ISO 4623-2 or EN 3665. Using the previously calibrated digital optical-imaging system, take a picture of the test panel
36、 area containing the scribe and the adjacent damaged area. After suitable threshold setting and damage detection, the digital image provides a value for the damaged area including the area of the scribe. The length of the scribe in the area assessed shall also be determined and indicated in the test
37、 report. If the damaged areas at the ends of the scribe differ from the remaining damaged area, these areas are not assessed. If the test panel contains several scribes (e.g. two intersecting scribes), these can be considered as sections of a single scribe, and the relevant areas and scribe lengths
38、can be added to one another. The area of intersection is not assessed. In the case of scribes perpendicular to each other, indicate the result for both scribes separately, as the scribe running perpendicular to the direction of rolling will show considerably more and longer filiform corrosion than t
39、hat running parallel to it. If the scribe width is not known, it shall be measured. If it cannot be measured, the same value (preferably zero) shall be used for all assessments intended to be comparative, and this value shall be quoted in the test report. BS EN ISO 21227-4:2008ISO 21227-4:2008(E) IS
40、O 2008 All rights reserved 38 Image evaluation In contrast to the manual assessment of filiform corrosion, digital optical imaging can determine directly the size of an area of any shape (see Figure 1). The assessment will thus be more accurate and more reproducible. a) Original image b) Binary imag
41、e Key w width of scribe l scribe length evaluated Llmaximum filament length on left-hand side of scribe Lrmaximum filament length on right-hand side of scribe Figure 1 Images showing parameters required for assessment BS EN ISO 21227-4:2008ISO 21227-4:2008(E) 4 ISO 2008 All rights reservedAssuming t
42、he scribe width w is known, calculate the area A of the scribe using Equation (1): A wl= (1) Calculate the mean width of the filiform corrosion fA, in millimetres, using Equation (2): 1A12AAfl= (2) where A is the area of the scribe, in square millimetres; A1is the area of the filiform corrosion, inc
43、luding the scribe area, in square millimetres; l is the scribe length evaluated, in millimetres. In the case of corrosion involving filaments of irregular length, an extended evaluation in accordance with Annex A is recommended in addition to the above. 9 Precision Information on the precision of th
44、is method is currently not available. 10 Test report The test report shall contain at least the following information: a) all information necessary for identification of the coating tested (manufacturer, trade name, batch number, etc.); b) a reference to this part of ISO 21227 (ISO 21227-4:2008); c)
45、 the type of illumination used (light source, arrangement of lamps); d) the image acquisition set-up used, including details of the 1) original image, 2) optical components used, 3) resolution, 4) image size, 5) grey level/colour depth, 6) gamma correction; e) details of the image processing and ima
46、ge analysis, including all processing procedures (filters) used; f) the scribe length evaluated; g) the result of the assessment, as indicated in Clause 8; BS EN ISO 21227-4:2008ISO 21227-4:2008(E) ISO 2008 All rights reserved 5h) any deviations from the procedure specified; i) any unusual features
47、(anomalies) observed during the test; j) the date of the test; k) the name of the person who carried out the test. BS EN ISO 21227-4:2008ISO 21227-4:2008(E) 6 ISO 2008 All rights reservedAnnex A (informative) Extended evaluation In the case of irregular corrosion, the degree of corrosion can be char
48、acterized more closely by reporting the following additional parameters: a) The so-called g-value, which is a measure of the irregularity of the corrosion and is given by Equation (A.1): ()1lrA AgL Ll=+(A.1) where A is the area of the scribe, in square millimetres; A1is the area of filiform corrosio
49、n, including the scribe area, in square millimetres; Llis the maximum length of the filaments on the left-hand side of the scribe, in millimetres; Lris the maximum length of the filaments on the right-hand side of the scribe, in millimetres; l is the scribe length, in millimetres. A large g-value is obtained when there are many uniform filaments (as in the case of infiltration of a protective coating by water), the maximum value being 1. A low g-value is obtained when there is a high degree of irregula
