EN ISO 2808:2007

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Paints and varnishes - Determination of film thickness (ISO 2808:2007)Barve in laki - Ugotavljanje debeline plasti (ISO 2808:2007)Peintures et vernis - Détermination de l'épaisseur du feuil (ISO 2808:2007)Beschichtungsstoffe - Bestimmung der Schichtdicke (ISO 2808:2007)Ta slovenski standard je istoveten z:EN ISO 2808:2007SIST EN ISO 2808:2007en;fr;de87.040Barve in lakiPaints and varnishesICS:SIST EN ISO 2808:19991DGRPHãþDSLOVENSKI
STANDARDSIST EN ISO 2808:200701-julij-2007

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN ISO 2808February 2007ICS 87.040Supersedes EN ISO 2808:1999
English VersionPaints and varnishes - Determination of film thickness (ISO2808:2007)Peintures et vernis - Détermination de l'épaisseur du feuil(ISO 2808:2007)Beschichtungsstoffe - Bestimmung der Schichtdicke (ISO2808:2007)This European Standard was approved by CEN on 16 December 2006.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 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 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, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, 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© 2007 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 2808:2007: E

Foreword
This document (EN ISO 2808:2007) has been prepared by Technical Committee 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 latest by August 2007, and conflicting national standards shall be withdrawn at the latest by August 2007.
This document supersedes EN ISO 2808:1999.
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, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Endorsement notice
The text of ISO 2808:2007 has been approved by CEN as EN ISO 2808:2007 without any modifications.

Reference numberISO 2808:2007(E)© ISO 2007
INTERNATIONAL STANDARD ISO2808Fourth edition2007-02-01Paints and varnishes — Determination of film thickness Peintures et vernis — Détermination de l'épaisseur du feuil

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ISO 2808:2007(E) © ISO 2007 – All rights reserved iiiContents Page Foreword.v Introduction.vi 1 Scope.1 2 Normative references.1 3 Terms and definitions.1 4 Determination of wet-film thickness.3 4.1 General.3 4.2 Mechanical methods.3 4.2.1 Principle.3 4.2.2 Field of application.3 4.2.3 General.3 4.2.4 Method 1A — Comb gauge.4 4.2.5 Method 1B — Wheel gauge.5 4.2.6 Method 1C — Dial gauge.6 4.3 Gravimetric method.7 4.3.1 Principle.7 4.3.2 Field of application.7 4.3.3 General.7 4.3.4 Method 2 — By difference in mass.7 4.4 Photothermal method.8 4.4.1 Principle.8 4.4.2 Field of application.8 4.4.3 General.9 4.4.4 Method 3 — Determination using thermal properties.9 5 Determination of dry-film thickness.9 5.1 General.9 5.2 Mechanical methods.9 5.2.1 Principle.9 5.2.2 Field of application.10 5.2.3 General.10 5.2.4 Method 4A — By difference in thickness.11 5.2.5 Method 4B — Depth gauging.13 5.2.6 Method 4C — Surface profile scanning.15 5.3 Gravimetric method.16 5.3.1 Principle.16 5.3.2 Field of application.16 5.3.3 General.16 5.3.4 Method 5 — By difference in mass.16 5.4 Optical methods.17 5.4.1 Principle.17 5.4.2 Field of application.18 5.4.3 General.18 5.4.4 Method 6A — Cross-sectioning.19 5.4.5 Method 6B — Wedge cut.20 5.5 Magnetic methods.20 5.5.1 General.20 5.5.2 Principle.20 5.5.3 Field of application.20 5.5.4 General.21

ISO 2808:2007(E) iv © ISO 2007 – All rights reserved 5.5.5 Method 7A — Magnetic pull-off gauge.21 5.5.6 Method 7B — Magnetic-flux gauge.22 5.5.7 Method 7C — Magnetic-induction gauge.22 5.5.8 Method 7D — Eddy-current gauge.23 5.6 Radiological method.24 5.6.1 Principle.24 5.6.2 Field of application.24 5.6.3 General.24 5.6.4 Method 8 — Beta backscatter method.25 5.7 Photothermal method.25 5.7.1 Principle.25 5.7.2 Field of application.26 5.7.3 General.26 5.7.4 Method 9 — Determination using thermal properties.27 5.8 Acoustic method.27 5.8.1 Principle.27 5.8.2 Field of application.27 5.8.3 General.27 5.8.4 Method 10 — Ultrasonic thickness gauge.28 6 Determination of thickness of uncured powder layers.28 6.1 General.28 6.2 Gravimetric method.29 6.2.1 Principle.29 6.2.2 Field of application.29 6.2.3 General.29 6.2.4 Method 11 — By difference in mass.29 6.3 Magnetic methods.29 6.3.1 Principle.29 6.3.2 Field of application.29 6.3.3 General.30 6.3.4 Method 12A — Magnetic-induction gauge.30 6.3.5 Method 12B — Eddy-current gauge.31 6.4 Photothermal method.31 6.4.1 Principle.31 6.4.2 Field of application.31 6.4.3 General.31 6.4.4 Method 13 — Determination using thermal properties.31 7 Measurement of film thickness on rough surfaces.32 7.1 General.32 7.2 Apparatus and materials.33 7.3 Procedure.33 7.3.1 Verification.33 7.3.2 Measurement.33 7.3.3 Number of readings.33 8 Test report.33 Annex A (informative)
Overview of methods.35 Bibliography.38

ISO 2808:2007(E) © ISO 2007 – All rights reserved vForeword 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 2808 was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee SC 9, General test methods for paints and varnishes. This fourth edition cancels and replaces the third edition (ISO 2808:1997), which has been technically revised. The main changes are as follows: a) The structure of the standard has been changed into four main clauses: 1) determination of wet-film thickness; 2) determination of dry-film thickness; 3) determination of the thickness of uncured powder layers; and 4) measurement of film thickness on rough surfaces. b) Methods using photothermal, radiological and acoustic techniques have been added. c) The split-beam method has been deleted as such instruments are no longer manufactured.

ISO 2808:2007(E) vi © ISO 2007 – All rights reserved Introduction Measurement of film thickness depends on the following steps: a) calibration of the measurement instrument, typically performed by the manufacturer or by any qualified laboratory; b) verification of the instrument (an accuracy check performed by the user at regular intervals, typically before each series of measurements); c) subsequent adjustment, if necessary, of the instrument so that the thickness readings it gives match those of a specimen of known thickness. For a dry-film thickness gauge this would mean zeroing it on the uncoated surface, using devices of known thickness such as shims, or using a coated specimen of known film thickness; d) measurement.

INTERNATIONAL STANDARD ISO 2808:2007(E) © ISO 2007 – All rights reserved 1Paints and varnishes — Determination of film thickness 1 Scope This International Standard describes a number of methods that are applicable to the measurement of the thickness of coatings applied to a substrate. Methods for determining wet-film thickness, dry-film thickness and the film thickness of uncured powder layers are described. Reference is made to individual standards where these exist. Otherwise the method is described in detail. An overview on the methods is given in Annex A, in which the field of application, existing standards and the precision are specified for the individual methods. This International Standard also defines terms concerning the determination of film thickness. 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 463, Geometrical Product Specifications (GPS) — Dimensional measuring equipment — Design and metrological characteristics of mechanical dial gauges ISO 3611, Micrometer callipers for external measurement ISO 4618:2006, Paints and varnishes — Terms and definitions ISO 8503-1, Preparation of steel substrates before application of paints and related products — Surface roughness characteristics of blast-cleaned steel substrates — Part 1: Specifications and definitions for ISO surface profile comparators for the assessment of abrasive blast-cleaned surfaces 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 4618 and the following apply. 3.1 substrate surface to which a coating material is applied or is to be applied [ISO 4618:2006] 3.2 coating continuous layer formed from a single or multiple application of a coating material to a substrate [ISO 4618:2006]

ISO 2808:2007(E) 2 © ISO 2007 – All rights reserved 3.3 film thickness distance between the surface of the film and the surface of the substrate 3.4 wet-film thickness thickness of a freshly applied wet coating material, measured immediately after application 3.5 dry-film thickness thickness of a coating remaining on the surface when the coating has hardened 3.6 thickness of uncured powder layer thickness of a freshly applied coating material in powder form, measured immediately after application and before stoving 3.7 relevant surface area1) part of an article covered or to be covered by the coating and for which the coating is essential for serviceability and/or appearance 3.8 test area1) representative part of the relevant surface area within which an agreed number of single measurements is made as a spot-check 3.9 measurement area1) area over which a single measurement is made 3.10 minimum local film thickness1) lowest value of the local film thickness found on the relevant surface area of a particular test specimen 3.11 maximum local film thickness1) highest value of the local film thickness found on the relevant surface area of a particular test specimen 3.12 mean film thickness1) arithmetic mean of all the individual dry-film thicknesses in the test area or the result of a gravimetric determination of the thickness 3.13 calibration controlled and documented process of measuring traceable calibration standards and verifying that the results are within the stated accuracy of the measurement instrument NOTE Initial calibration is typically performed by the instrument manufacturer or by a qualified laboratory in a controlled environment using a documented process. This initial calibration will normally be verified by the user at regular intervals. The standards used in the calibration are such that the combined uncertainties of the resultant measurement are less than the stated accuracy of the instrument.
1) Measurement of this property is only required for the extended evaluation of film thickness measurements; see Clause 8 (test report), items k) and l).

ISO 2808:2007(E) © ISO 2007 – All rights reserved 33.14 verification accuracy check performed by the user using reference standards 3.15 reference standard specimen of known thickness against which a user can verify the accuracy of the measurement instrument NOTE Reference standards may be coated thickness standards, or shims. If agreed to by the contracting parties, a part of the test specimen may be used as a thickness standard for a particular job. 3.16 adjustment act of aligning the measurement instrument's thickness readings to match those of a reference standard NOTE Most electronic measurement instruments can be adjusted on a thickness standard or on a shim, where the thickness of the coating or of the shim is known. 3.17 accuracy consistency between a measured value and the true value of the thickness standard 4 Determination of wet-film thickness 4.1 General Annex A gives an overview of the methods used for the determination of wet-film thickness. 4.2 Mechanical methods 4.2.1 Principle In all mechanical methods the substrate surface is contacted by part of the measurement instrument through the coating, and the surface of the coating is contacted simultaneously (see Figure 1) or subsequently (see Figures 2 and 3) by another part of the instrument. The wet-film thickness is the height difference between these two points of contact, which can be read directly. 4.2.2 Field of application The mechanical principle is suitable for all film-substrate combinations. The substrate has to be flat in at least one direction in the area where the measurement is conducted. Curvature of the surface in a single plane is permissible (e.g. internal or external surface of pipes). 4.2.3 General Classification as a destructive or non-destructive method depends on: a) the rheological properties of the coating material; b) the nature of the wetting contact between the contact surfaces of the measurement instrument and the coating material; c) whether the thickness measurements will make the coating unsuitable for the purpose for which it is intended. Since the possibility of pigment particles remaining between the gauge and the substrate cannot be excluded, all mechanical methods contain a systematic error: the film thickness displayed is smaller than the actual wet-film thickness by at least the mean diameter of the pigment particles.

ISO 2808:2007(E) 4 © ISO 2007 – All rights reserved In the case of a wheel gauge (method 1B, see 4.2.5), the wheel has to be wetted by the coating material. If not, this represents a further source of systematic error which can result in exaggerated readings and is a function of: ⎯ the surface tension and the rheological properties of the coating material; ⎯ the material of the wheel gauge; ⎯ the speed at which the wheel is turned. 4.2.4 Method 1A — Comb gauge 4.2.4.1 Description of instrument A comb gauge is a flat plate made of a corrosion-resistant material with teeth along its edges (see Figure 1). The reference teeth at the corners of the plate define a baseline along which the inner teeth are arranged to give a graduated series of gaps. Each tooth is labelled with the assigned gap value. With commercially available comb gauges the maximum thickness which can be measured is typically 2 000 µm and the smallest increment is typically 5 µm.
Key 1 substrate 2 coating 3 point of wetting contact 4 comb gauge Figure 1 — Example of a comb gauge 4.2.4.2 Procedure Ensure that the teeth are clean and not worn or damaged. Place the comb gauge onto the flat specimen surface such that the teeth are normal to the plane of the surface. Allow sufficient time for the coating to wet the teeth prior to removing the gauge. In the case of specimens curved in a single plane, the comb gauge shall be placed in position parallel to the axis of curvature. The result of the thickness measurement depends on the time of measurement. The thickness should therefore be measured as soon as possible after application. Note the greatest gap reading of the tooth wetted by the coating material as the wet-film thickness.

ISO 2808:2007(E) © ISO 2007 – All rights reserved 54.2.5 Method 1B — Wheel gauge 4.2.5.1 Description of instrument A wheel gauge consists of a wheel, made of hardened and corrosion-resistant steel, with three projecting rims (see Figure 2). Two rims are ground to the same diameter and are configured concentrically to the wheel axle. The third rim has a smaller diameter and is eccentrically ground. One of the outer rims has a scale from which the respective projection of the concentric rims relative to the eccentric rim can be read. Two versions are available: ⎯ version 1 has the eccentric rim located between the concentric rims; ⎯ version 2 has the eccentric rim located outside the concentric rims and closely adjacent to one of them. NOTE Unlike version 1, the design of version 2 allows parallax-free reading of the wet-film thickness. With commercially available wheel gauges, the maximum thickness which can be measured is typically 1 500 µm and the smallest increment is typically 2 µm.
Key 1 substrate 2 coating 3 eccentric rim 4 wheel gauge Figure 2 — Example of a wheel gauge 4.2.5.2 Procedure Grip the wheel gauge with the thumb and index finger by the wheel axle and press the concentric rims onto the surface at the point of the largest reading on the scale. In the case of specimens curved in a single plane, the axis of curvature and the wheel gauge axle shall be parallel. Roll the wheel gauge in one direction, lift it from the surface and read off the highest scale reading at which the eccentric rim is still wetted by the coating material. Clean the gauge and repeat in the other direction.

ISO 2808:2007(E) 6 © ISO 2007 – All rights reserved Calculate the wet-film thickness as the arithmetic mean of these readings. The result of the thickness measurement depends on the time of measurement. The thickness should therefore be measured as soon as possible after application. To minimize the effect of surface tension on the result, observe how the paint wets the eccentric rim and record the scale reading at the first point of contact. This is only possible with version 2 of the wheel gauge. 4.2.6 Method 1C — Dial gauge 4.2.6.1 Instrument and reference standards 4.2.6.1.1 Dial gauge (see Figure 3) Mechanical dial gauges conforming to the requirements of ISO 463 and electronic dial gauges are typically capable of measuring to an accuracy of 5 µm (mechanical dial gauge) or 1 µm (electronic dial gauge), or better. The gauge can have an analogue or digital display. The underside of the dial gauge has two contact pins of equal length located equidistant from the movable plunger and in a straight line with it. An adjusting screw is used to make fine adjustments to the position of the plunger in its guideway.
Key 1 substrate 2 coating 3 plunger Figure 3 — Example of a dial gauge 4.2.6.1.2 Reference standard for zeroing the gauge A flat reference plate is required for zeroing the gauge. The reference plate shall consist of a flat glass plate whose flatness tolerance does not exceed 1 µm (see also ISO 1101 [1]). 4.2.6.2 Procedure Zero the dial gauge on the reference plate with the measuring tip adjusted so that it is just touching the plate. Screw the plunger back from the zeroing position. Place the contact pins of the dial gauge on the specimen so that they are normal to the surface of the substrate and carefully screw the plunger down until the measuring tip is just touching the coating material.

ISO 2808:2007(E) © ISO 2007 – All rights reserved 7The result of the thickness measurement depends on the time of measurement. The thickness should therefore be measured as soon as possible after application. Read the wet-film thickness directly from the gauge. 4.3 Gravimetric method 4.3.1 Principle A coating is applied and the thickness is determined by dividing the mass of the coating by its density and by the coated surface area. The wet-film thickness, tw, in micrometres, is calculated from the equation 0wmmtAρ−=⋅ (1) where m0 is the mass of the uncoated specimen, in grams; m is the mass of the coated specimen, in grams; A is the coated surface area, in square metres; ρ is the density of the liquid coating material applied, in grams per millilitre. NOTE The density of the liquid coating material applied can be determined in accordance with ISO 2811-1, ISO 2811-2, ISO 2811-3 or ISO 2811-4. 4.3.2 Field of application The gravimetric principle is generally applicable, provided that the amount of highly volatile substances in the liquid coating material is low. 4.3.3 General Determination using the gravimetric principle yields the mean value of the wet-film thickness over the entire coated surface area. With spray application in particular, the reverse side of the specimen shall be masked to prevent measurement errors resulting from partial coating of the reverse (overspray). Any masking of the reverse side shall be removed before weighing the coated specimen. 4.3.4 Method 2 — By difference in mass 4.3.4.1 Apparatus Required are scales capable of weighing up to 500 g to the nearest 1 mg. 4.3.4.2 Procedure Weigh the specimen first uncoated and then coated and calculate the wet-film thickness using Equation (1).

ISO 2808:2007(E) 8 © ISO 2007 – All rights reserved 4.4 Photothermal method 4.4.1 Principle The film thickness is determined from the difference between the time a thermal wave is radiated towards the coating and the time the re-emitted wave (either heat or ultrasonic) is detected (see Figure 4). Irrespective of the type of excitation involved or the method of detection, all photothermal methods use the same principle: the periodic or pulsed introduction of energy in the form of heat into a specimen and the subsequent detection of the local temperature increase. The time difference measured is compared against values obtained with the instrument for films of known thickness under fixed conditions (excitation energy, pulse length, excitation frequency, etc.) (see 4.4.4.2).
Key 1 substrate 2 coating 3 re-emitted thermal radiation 4 absorption of radiation by coating (depends on coating thickness and coating material) 5 thermal irradiation 6 thermal waves 7 ultrasonic waves 8 surface deformation Figure 4 — Interaction of radiation with the specimen in photothermal thickness measurement, showing surface deformation
4.4.2 Field of application The photothermal principle is basically suitable for all film-substrate combinations. It can also be used to determine the thicknesses of the individual layers in a multilayer coating, provided the layers are sufficiently distinct from each other with respect to their thermal conductivity and reflection properties. The required minimum substrate thickness is a function of the measurement system used (see 4.4.4.1.1) and the film-substrate combination.

ISO 2808:2007(E) © ISO 2007 – All rights reserved 94.4.3 General Classification of the method as destructive or non-destructive depends on the purpose of the coating. The thermal energy absorbed by the coating could have an impact on the coating owing to the local heating effect produced (see item 8 in Figure 4). 4.4.4 Method 3 — Determination using thermal properties 4.4.4.1 Instrument and reference standards 4.4.4.1.1 Measurement system There are various methods for producing thermal waves in a coating material and for detecting the thermal effects induced at the heated location in the specimen (see EN 15042-2 [18]). Thermal radiation sources (e.g. laser sources, light-emitting diodes, incandescent light sources) are mainly used as the excitation system for paint coatings. The following detection methods are used: ⎯ detection of the re-emitted thermal radiation (photothermal radiometry); ⎯ detection of the change in refractive index (in the heated air above the measurement area); ⎯ pyroelectric detection (heat flow measurement). 4.4.4.1.2 Reference standards Reference specimens with different absorption properties and a range of film thicknesses are required for calibration purposes (see EN 15042-2 [18]). 4.4.4.2 Calibration Calibrate the measurement system with the reference specimens (see 4.4.4.1.2) for each film-substrate combination (in particular for each coating material). 4.4.4.3 Procedure Operate the apparatus and measure the film thickness in accordance with the manufacturer's instructions. 5 Determination of dry-film thickness 5.1 General Annex A gives an overview of the methods used for determination of dry-film thickness. 5.2 Mechanical methods 5.2.1 Principle A micrometer or dial gauge (method 4A, see 5.2.4) is used to measure the film thickness as the difference between the total thickness (substrate + film) and the substrate thickness.

ISO 2808:2007(E) 10 © ISO 2007 – All rights reserved There are two ways of determining the film thickness: a) Measurements are made before and after coating removal (destructive) The total thickness is first measured in a defined measurement area and then, after the coating has been removed in the measurement area, the substrate thickness is measured. b) Measurements are made before and after coating application (non-destructive) The substrate thickness is first measured and then the total thickness is measured in the same measurement area after coating. The film thickness is calculated from the difference between the two readings. A depth gauge (method 4B, see 5.2.5) or a profilometer (method 4C, see 5.2.6) enable the film thickness to be determined directly as the difference in height between the surface of the film and the surface of the exposed substrate. NOTE Only the “coating removal” variant is possible with a depth gauge or profilometer (methods 4B and 4C). 5.2.2 Field of application The mechanical principle is basically suitable for all film-substrate combinations. Where mechanical gauging is used, the substrate and coating shall be hard enough to prevent the reading from being falsified as a result of the measuring tip creating an indentation. The micrometer or dial gauge (method 4A) is also suitable for measuring the film thickness of cylindrical specimens of circular cross-section (e.g. wires, pipes). The profilometer (method 4C) is recognized as the referee method in the event of disputes. 5.2.3 General In the “coating application” variant, a template with labelled holes is used to ensure that the determination of the substrate thickness and total thickness is carried out at exactly the same points. NOTE 1 The “coating application” variant is preferred in the case of plastic substrates since in most cases the substrate cannot be exposed without causing damage. In the “coating removal” variant, the measurement areas shall be circled and labelled. The coating shall be carefully and completely removed in the measurement areas without damaging the substrate mechanically or chemically. The substrate may be partly masked using adhesive tape before coating in order to obtain well-defined steps from one layer to the next. In the case of the depth gauge and profilometer (methods 4B and 4C), the coating which is not removed in the region of the measurement area shall remain undamaged. In the case of the profilometer (method 4C), the shoulder between the substrate and the film surface shall be sufficiently well defined. With hard substrates (e.g. glass) the coating can be removed mechanically, but with less hard substrates (e.g. steel) the coating shall be removed chemically using a solvent or paint remover. NOTE 2 In the case of less hard substrate materials such as steel, the film can be cut through with a core drill of 10 mm diameter and the disc of coating thus formed removed with a solvent or paint remover. All surfaces (coating, substrate, reverse side of specimen) which are contacted or gauged shall be clean and free from film residues.

ISO 2808:2007(E) © ISO 2007 – All rights reserved 115.2.4 Method 4A — By difference in thickness 5.2.4.1 Description of instrument 5.2.4.1.1 Micrometer The micrometer shall be capable of measuring to the nearest 5 µm. It shall be fitted with a ratchet to limit the force exerted by the spindle on the test surface. Version 1 — Fixed to a stand A micrometer head with a plane measuring face is clamped to a rigid stand with a flat baseplate such that its height can be adjusted. The measuring face shall be aligned parallel to the top of the baseplate. Version 2 — Hand-held (see Figure 5) The usual term for this kind of instrument is an outside micrometer, although it is also known as micrometer callipers for exterrnal use (see ISO 3611). The micrometer shall conform to the requirements of ISO 3611. The measuring faces of the spindle and the anvil shall be plane and parallel to each other.
Figure 5 — Outside micrometer
5.2.4.1.2 Dial gauge Mechanical dial gauges conforming to the requirements of ISO 463 and electronic dial gauges are typically capable of measuring to an accuracy of 5 µm (mechanical dial gauge) or 1 µm (electronic dial gauge), or better. The gauge shall be fitted with a device for lifting the measuring tip. The shape of the measuring tip shall be selected as a function of the hardness of the coating material whose thickness is to be measured (spherical for hard materials, plane for soft materials). Version 1 — Fixed to a stand The dial gauge is clamped to a stand as shown in Figure 6. If a plane stylus tip is used, the measurement surface shall be aligned parallel to the top of the baseplate.

ISO 2808:2007(E) 12 © ISO 2007 – All rights reserved
Figure 6 — Dial gauge fixed to a stand
Version 2 — Hand-held This dial gauge is fitted with a hand grip. The device for lifting the plunger shall be configured such that the thickness gauge can be operated with one hand. The interchangeable tip of the anvil shall be located opposite the movable measuring tip. The shape of the measuring tip shall be selected as a function of the hardness of the material to be tested (spherical for hard materials, plane for soft materials). If both the measuring tip and the anvil are of plane design (such as in the foil thickness gauge shown in Figure 7), the measurement surfaces shall be parallel to each other.
Key 1 gauge aperture Figure 7 — Foil thickness gauge

ISO 2808:2007(E) © ISO 2007 – All rights reserved 135.2.4.2 Procedure Prepare the specimen as specified in 5.2.3 for the “coating removal” and “coating application” variants (see 5.2.1). Ope
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