SIST EN ISO 2177:2004

Metallic coatings - Measurement of coating thickness - Coulometric method by anodic dissolution (ISO 2177:2003)

ISO 2177:2002 describes a coulometric method by anodic dissolution for measuring the thickness of metallic coatings. It is only applicable to conductive coatings.
Typical combinations of coatings and substrates that can be tested by this method are given. Other combinations may be tested with electrolytes in current use, or new electrolytes may be developed for them but, in both cases, it is necessary to verify the suitability of the complete system.
ISO 2177:2002 is also applicable to multi-layer systems, e.g Cu-Ni-Cr. It may be used to measure the thickness of coatings applied by various means, if due account is taken of special features such as the presence of an alloy layer. In some cases, the presence and thickness of diffusion layers can also be measured. It can also be used to measure the thickness of coatings on cylindrical specimens and wires.

Metallische Überzüge - Schichtdickenmessung - Coulometrisches Verfahren durch anodisches Ablösen (ISO 2177:2003)

Diese internationale Norm beschreibt ein coulometrisches Verfahren, bei dem durch anodisches Ablösen die Dicke metallischer Schichten gemessen wird.
Typische Systeme von Schicht- und Substratwerkstoffen, die nach diesem Verfahren gemessen werden können, sind in Tabelle 1 angegeben.
Andere Kombinationen können mit gebräuchlichen Elektrolyten (siehe Anhang A) gemessen werden oder es können neue Elektrolyte dafür entwickelt werden. In beiden Fällen ist es jedoch notwendig, die Eignung des Gesamtsystems zu überprüfen.
Die Norm ist auch für Mehrschichtsysteme, z. B. Cu/Ni/Cr, anwendbar (siehe auch 8.5).
Das Verfahren kann zur Messung der Dicke von Schichten eingesetzt werden, die auf verschiedene Weise aufgebracht wurden, wenn spezielle Eigenschaften (wie z. B. durch eine vorhandene Legierungsschicht) berücksichtigt werden. In einigen Fällen kann auch das Vorhandensein und die Dicke von Diffusionsschichten gemessen werden. Es sind auch Schichtdickenmessungen an zylindrischen Proben und Drähten möglich (siehe 8.7).

Revetements métalliques - Mesurage de l'épaisseur - Méthode coulométrique par dissolution anodique (ISO 2177:2003)

L'ISO 2177:2002 décrit une méthode coulométrique de mesurage, par dissolution anodique, de l'épaisseur des revêtements métalliques. Elle n'est applicable qu'aux dépôts conducteurs.
Elle donne des combinaisons types de dépôts et de métaux de base qui peuvent être mesurés selon cette méthode. D'autres combinaisons peuvent être essayées avec des électrolytes d'usage courant, ou avec de nouveaux électrolytes mis au point à cet effet mais il est, dans les deux cas, nécessaire de vérifier l'aptitude à l'emploi du système complet.
L'ISO 2177:2002 est également applicable aux systèmes multicouches, par exemple Cu-Ni-Cr. Elle peut aussi être utilisée pour mesurer l'épaisseur de revêtements appliqués par divers moyens, s'il est tenu compte des particularités telles que la présence d'une couche d'alliage. Dans certains cas, il est également possible de déceler la présence et de mesurer l'épaisseur de couches de diffusion. Elle peut enfin être utilisée pour mesurer l'épaisseur des revêtements déposés sur des échantillons cylindriques et des fils.

Kovinske prevleke - Merjenje debeline prevleke - Kulometrična metoda z anodnim raztapljanjem (ISO 2177:2003)

General Information

• Status: Published
• Publication Date: 31-Aug-2004
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: IPKZ - Protection of metals against corrosion
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Sep-2004
• Due Date: 01-Sep-2004
• Completion Date: 01-Sep-2004
• Ref Project: EN ISO 2177:2004 - Metallic coatings - Measurement of coating thickness - Coulometric method by anodic dissolution (ISO 2177:2003)

Relations

• Replaces: SIST EN ISO 2177:1999 - Metallic coatings - Measurement of coating thickness - Coulometric method by anodic dissolution (ISO 2177:1985)
• Effective Date: 01-Dec-2004

Overview

EN ISO 2177:2004 (identical to ISO 2177:2003) specifies a coulometric method by anodic dissolution for measuring the thickness of metallic coatings. The method is applicable only to conductive coatings, including multi-layer systems (e.g., Cu–Ni–Cr) and coatings on cylindrical specimens and wires. Thickness is determined from the quantity of electricity (coulombs) required to anodically dissolve a defined test area; an endpoint is detected by a change in cell voltage.

Key topics and technical requirements

• Scope and applicability
  • Designed for conductive metallic coatings; typical coating/substrate pairs are listed in the standard.
  • Other combinations can be tested with existing or newly developed electrolytes, but the suitability of the complete system must be verified before use.
• Principle
  • A sealed measuring area is anodically dissolved in a suitable electrolyte. Thickness is calculated from either constant-current × time or the integrated charge.
  • Endpoint detection relies on a detectable change in electrode potential when the substrate is exposed.
• Instrumentation
  • Proprietary and custom instruments are used (see Annex B). Instruments may give direct readout or provide recorded charge (coulombs) for conversion to thickness.
  • Instruments must be checked against specimens of known thickness; agreement within ±5 % allows use without adjustment.
• Electrolyte
  • Electrolyte selection (Annex A) must ensure high anodic dissolution efficiency, wetting of the test area and a stable shelf-life.
  • Electrolyte choice depends on coating/substrate materials, current density and cell circulation.
• Factors affecting accuracy
  • Coating thickness limits (practical accuracy reduced for >50 µm and <0.2 µm unless special equipment is used).
  • Current stability, measuring area accuracy (seal/gasket wear), agitation, alloy or diffusion layers, coating purity and surface condition.
• Multi-layer and special cases
  • Applicable to multi-layer coatings and can, in some cases, measure diffusion or alloy layers with appropriate care.

Applications and users

• Practical uses:
  • Quality control and production monitoring for electroplated and deposited metallic finishes.
  • Verification of coating processes (plating, electroforming, surface treatment) and R&D of coating systems.
  • Measurement on complex geometries including wires and cylindrical parts.
• Typical users:
  • Plating shops, surface-treatment laboratories, materials testing labs, OEM quality departments, and standards/inspection bodies.

Related standards

• ISO 2064 and ISO 2080 are normative references for definitions and vocabulary relevant to coating thickness measurement and surface treatment terminology.

Keywords: EN ISO 2177:2004, ISO 2177, coulometric method, anodic dissolution, coating thickness measurement, metallic coatings, electrolytes, instrumentation, quality control.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Metallische Überzüge - Schichtdickenmessung - Coulometrisches Verfahren durch anodisches Ablösen (ISO 2177:2003)Revetements métalliques - Mesurage de l'épaisseur - Méthode coulométrique par dissolution anodique (ISO 2177:2003)Metallic coatings - Measurement of coating thickness - Coulometric method by anodic dissolution (ISO 2177:2003)25.220.40Kovinske prevlekeMetallic coatingsICS:Ta slovenski standard je istoveten z:EN ISO 2177:2004SIST EN ISO 2177:2004en01-september-2004SIST EN ISO 2177:2004SLOVENSKI
STANDARDSIST EN ISO 2177:19991DGRPHãþD

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN ISO 2177May 2004ICS 25.220.40Supersedes EN ISO 2177:1994English versionMetallic coatings - Measurement of coating thickness -Coulometric method by anodic dissolution (ISO 2177:2003)Revêtements métalliques - Mesurage de l'épaisseur -Méthode coulométrique par dissolution anodique (ISO2177:2003)Metallische Überzüge - Schichtdickenmessung -Coulometrisches Verfahren durch anodisches Ablösen(ISO 2177:2003)This European Standard was approved by CEN on 1 April 2004.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-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the 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 responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2004 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 2177:2004 ESIST EN ISO 2177:2004

Normative references to International Standards are listed in Annex ZA (normative).SIST EN ISO 2177:2004

Reference numberISO 2177:2003(E)© ISO 2003
INTERNATIONAL STANDARD ISO2177Third edition2003-03-15Metallic coatings — Measurement of coating thickness —Coulometric method by anodic dissolution Revêtements métalliques — Mesurage de l'épaisseur — Méthode coulométrique par dissolution anodique
ISO 2177:2003(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
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ISO 2003 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body in the country of the requester. ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel.
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www.iso.org Published in Switzerland
ii © ISO 2003 — All rights reserved
ISO 2177:2003(E) © ISO 2003 — All rights reserved iii Contents Page Foreword.iv 1 Scope.1 2 Normative references.1 3 Terms and definitions.1 4 Principle.2 5 Instrumentation.2 6 Electrolyte.2 7 Factors affecting the measuring accuracy.3 7.1 Coating thickness.3 7.2 Current variation.3 7.3 Area variation.3 7.4 Agitation (if required).4 7.5 Alloy layer between coating and substrate.4 7.6 Purity of coatings.4 7.7 Condition of test surface.4 7.8 Density of coating material.4 7.9 Cleanliness of the cell.4 7.10 Cleanliness of electrical connections.4 7.11 Calibration standards (if used).4 7.12 Non-uniform dissolution.5 8 Procedure.5 8.1 General.5 8.2 Preparation of test surface.5 8.3 Cell application.5 8.4 Electrolysis.5 8.5 Undercoats.5 8.6 Examination after test.6 8.7 Coatings on cylindrical specimens.6 9 Expression of results.6 10 Measurement uncertainty.7 11 Test report.7 Annex A (informative)
Typical electrolytes.8 Annex B (informative)
Types of instrument.13
ISO 2177:2003(E) iv © ISO 2003 — All rights reserved Foreword 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. 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 liaison 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 technical 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 drawn 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 2177 was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings, Subcommittee SC 2, Test methods. This third edition cancels and replaces the second edition (ISO 2177:1985), which has been technically revised.
INTERNATIONAL STANDARD ISO 2177:2003(E) © ISO 2003 — All rights reserved 1 Metallic coatings — Measurement of coating thickness — Coulometric method by anodic dissolution 1 Scope This International Standard describes a coulometric method, by anodic dissolution, for measuring the thickness of metallic coatings. It is only applicable to conductive coatings. Typical combinations of coatings and substrates that can be tested by this method are given in Table 1. Other combinations may be tested with electrolytes in current use (see Annex A), or new electrolytes may be developed for them but, in both cases, it is necessary to verify the suitability of the complete system. This International Standard is also applicable to multi-layer systems, e.g Cu-Ni-Cr (see also 8.5). It may be used to measure the thickness of coatings applied by various means, if due account is taken of special features such as the presence of an alloy layer. In some cases, the presence and thickness of diffusion layers can also be measured. It can also be used to measure the thickness of coatings on cylindrical specimens and wires (see 8.7). 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. ISO 2064:1996, Metallic and other inorganic coatings — Definitions and conventions concerning the measurement of thickness ISO 2080, Surface treatment, metallic and other inorganic coatings — Vocabulary 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 2064 and ISO 2080 as well as the following apply. 3.1 measuring area area of the significant surface over which a single measurement is made NOTE The measuring area for this method is the area enclosed by the sealing ring of the cell. SIST EN ISO 2177:2004

ISO 2177:2003(E) 2 © ISO 2003 — All rights reserved 4 Principle A well-defined area of the coating is subjected to anodic dissolution using a suitable electrolyte. The virtually complete dissolution of the coating is detected by a change in cell voltage. The coating thickness is calculated from the quantity of electricity used, in coulombs, which in turn may be calculated from: a) the time interval between the start and the end of the test, if it is conducted at constant current density; b) the integrated quantity of electricity used in dissolving the coatings. 5 Instrumentation 5.1 Suitable instruments can be constructed from readily available components but proprietary instruments are usually used (see Annex B). 5.2 Proprietary direct-reading instruments are available for use with electrolytes recommended by the manufacturer. Other instruments record the quantity of electricity, in coulombs, used in dissolving the coating from the measuring area (see 3.1), usually in arbitrary units, from which the thickness is calculated using factors or tables. With direct reading instruments, the calculation of thickness from current density is made electronically. 5.3 The performance of the instrument shall be checked using specimens of known coating thickness. If the instrument readings agree to within ± 5 % of the known thicknesses of the specimens, the instrument may be used without further adjustment; otherwise, the cause of the discrepancy shall be removed. However, proprietary instruments shall always be calibrated in accordance with the manufacturer's instructions. Suitable specimens of known coating thickness shall consist of the same type of coating and substrate as the specimen to be measured, and they shall have an accuracy of 5 % or better. In measuring alloy coatings, the use of correct specimens is of particular importance. 6 Electrolyte The electrolyte shall have a known, adequate shelf-life and shall be such that: a) there is no reaction with the coating metal in the absence of an impressed flow of current; b) the coating dissolves anodically at an efficiency as close to 100 % as possible; c) a detectable change in electrode potential occurs as the coating is penetrated and an increasing area of substrate is exposed; d) the test area exposed in the test cell is completely wetted. The electrolyte shall be chosen with reference to the coating and substrate materials, the current density and electrolyte circulation within the test cell. NOTE Typical electrolytes that have been found satisfactory for use with one type of test apparatus for testing various electrodeposited coatings on specific substrates are described in Annex A. For proprietary instruments, the electrolytes shall normally be chosen on the recommendations of the manufacturer. SIST EN ISO 2177:2004

ISO 2177:2003(E) © ISO 2003 — All rights reserved 3 Table 1 — Typical combinations of coatings and substrates that can be tested
by the coulometric method Coating Substrate (underlying material)
Al a Cu and Cu alloys Ni Ni-Co-Fe alloys Ag Steel Zn Non-metals Cd × × × — — × — × Cr × × × — — × — × Cu × Only on brass and copper-beryllium × — — × × × Au × × × × × × — — Pb × × × × × ×
× Ni × × — × — × — × Ni, autocatalytic b × × × × — × — × Ag × × × — — × — × Sn × × × — — × — × Sn-Ni alloys — × — — — × — × Sn-Pb alloys c × × × × — × — × Zn × × × — — × — × a The detection of the change in the cell voltage may be difficult with some aluminium alloys. b The coulometric method can only be used if the phosphorus or boron contents of these coatings are within certain limits. c The method is sensitive to alloy composition. NOTE See Clause 5 for instrumentation. 7 Factors affecting the measuring accuracy 7.1 Coating thickness Generally, the accuracy is lower than optimum for coating thicknesses greater than 50 µm and less than 0,2 µm, unless special equipment is used. With coatings thicker than 50 µm, there may be an appreciable amount of bevelling or undercutting as the anodic dissolution proceeds. The amount of bevelling is largely dependent on the method employed for stirring the electrolyte. Undercutting may be eliminated, or reduced, by increasing the rate of dissolution, i.e. by increasing the current density used in the test. 7.2 Current variation For instrumentation using the constant-current and time-measuring technique, current variation causes errors. For instruments using a current-time integrator, too large a change in current may change the anode current efficiency and interfere with the end-point thus causing an error. 7.3 Area variation The accuracy of the thickness measurement will be no better than the accuracy to which the measuring area is known. Area variations due to gasket wear, gasket pressure, etc., may lead to measurement errors. Much greater accuracy can be obtained if the electrolytic cells are so designed that sealing rings consistently give SIST EN ISO 2177:2004

ISO 2177:2003(E) 4 © ISO 2003 — All rights reserved well defined measuring areas. In some cases it may be advantageous to measure the area after it has been de-plated and compensate accordingly. NOTE Error due to variations of the measuring area may, in some instances, be minimized by modifying the instrument calibration using coating thickness calibration standards. Such standards should create similar test conditions to those during actual tests, particularly if testing curved surfaces. 7.4 Agitation (if required) Inadequate agitation and over-agitation can cause a false end-point. 7.5 Alloy layer between coating and substrate The measurement of coating thickness by the coulometric method assumes implicitly that a sharply defined interface exists between the coating and the substrate. If an alloy layer exists between the coating and the substrate as, for example, in the case of coatings applied by hot dipping, the coulometric end-point can occur at some point within the alloy later, thus giving falsely high values for the thickness of the unalloyed coatings. See B.1.2. NOTE It is possible to use a potential recording chart recorder to detect the potential step where the alloy commences and also when the pure substrate is reached by the dissolution process. 7.6 Purity of coatings Materials that co-deposit with a coating metal (including alloying metals) can change the effective electrochemical equivalent of the coating metal, the anode current efficiency, and the coating density. 7.7 Condition of test surface Oil, grease, paint, corrosion products, polishing ingredients, conversion coatings, passivity of nickel coatings, etc., can interfere with the test. 7.8 Density of coating material Because the coulometric method measures intrinsically mass per unit area, variations in density from the normal density of the coating metal will cause corresponding variations in linear thickness measurements. Normal variations of the composition of an alloy result in small, but significant changes in alloy density and its electrochemical equivalent. 7.9 Cleanliness of the cell Deposition of metal can take place on the cathode in some electrolytes. This deposit can alter the cell voltages or block the cell aperture. It is, therefore, essential to keep the cathode clean. 7.10 Cleanliness of electrical connections In the case of instruments other than the constant current type, if the electrical connections are not clean, the current/potential relationship will be disturbed and false end-points obtained. 7.11 Calibration standards (if used) Measurements made using calibration standards are subject to the additional error of the standards. If the thickness of alloy coatings is being determined, it is usually necessary to use coating standards and to test them using the same procedure. NOTE The coating of the standards might not be similar to that being tested, e.g. zinc produced by an acid and by an alkali electroplating bath. SIST EN ISO 2177:2004

ISO 2177:2003(E) © ISO 2003 — All rights reserved 5 7.12 Non-uniform dissolution If the rate of dissolution is not uniform over the measuring area, a premature end-point can be obtained, and yield falsely low results. Hence, the surface shall be examined after the test to verify that most of the coating has dissolved. On some substrates however, a visible, but insignificant, portion of the coating may remain. The presence of other material in the coating, the roughness of the coating surface and interface and the presence of porosity in the coating can cause fluctuation of the cell voltage. Such fluctuations can prematurely affect the end-point. 8 Procedure 8.1 General If commercial equipment is used, follow the manufacturer's instructions with respect to the operating procedure for measurement, the electrolytes and, if necessary, calibration (see 5.3). Appropriate attention shall be given to the factors listed in Clause 7. NOTE If using instruments that require a pre-set voltage, it should be noted that the actual value is dependent on the particular metallic coating, current density, electrolyte concentration and temperature and circuit resistance, e.g. lead-out connections. For these reasons, it is considered advisable to first perform an evaluation test. 8.2 Preparation of test surface The test surface (see 7.7) shall be cleaned immediately p
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