INTERNATIONAL STANDARD ISO 16962 Second edition 2017-02 Surface chemical analysis — Analysis of zinc- and/or aluminium-based metallic coatings by glow-discharge optical-emission spectrometry Analyse chimique des surfaces — Analyse des revêtements métalliques base de zinc et/ou d’aluminium par spectrométrie d’émission optique décharge luminescente Reference number ISO 16962:2017(E) © ISO 2017 ISO 16962:2017(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2017, Published in Switzerland All rights reserved Unless otherwise specified, no part o f this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission Permission can be requested from either ISO at the address below or ISO’s member body in the country o f the requester ISO copyright o ffice Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii © ISO 2017 – All rights reserved ISO 16962:2017(E) Page Contents Foreword v Introduction vi Scope Normative references Terms and definitions Principle Apparatus Adjusting the glow-discharge spectrometer system settings 5.1 6.1 6.2 6.3 6.4 Glow-discharge optical-emission spectrometer 5.1.1 General 5.1.2 Selection of spectral lines 5.1.3 Selection o f glow-discharge source type General Setting the parameters of a DC source 6.2.1 Constant applied current and voltage 6.2.2 Constant applied current and pressure 6.2.3 Constant voltage and pressure Setting the discharge parameters of an RF source 6.3.1 General 6.3.2 Constant applied power and pressure 6.3.3 Constant applied power and DC bias voltage 6.3.4 Constant effective power and effective RF voltage Minimum performance requirements 6.4.1 General 6.4.2 Minimum repeatability 6.4.3 Detection limit Sampling Calibration 8.1 8.2 8.3 8.4 8.5 8.6 8.7 General Calibration samples 10 8.2.1 General 10 8.2.2 Brass calibration samples 10 8.2.3 Zn-Al alloy samples 10 8.2.4 Low alloy iron or steel samples 10 8.2.5 Stainless steel samples 10 8.2.6 Nickel alloy samples 10 8.2.7 Aluminium-silicon alloy samples 10 8.2.8 Aluminium-magnesium alloy samples 10 8.2.9 High-purity copper and zinc samples 11 Validation samples and optional RMs for calibration 11 8.3.1 General 11 8.3.2 Zinc-nickel electrolytically coated RM 11 8.3.3 Zinc-iron electrolytically coated RM 11 8.3.4 Zinc-aluminium hot dip coated RM 11 8.3.5 Zinc-iron hot dip coated and annealed RM 11 Determination of the sputtering rate of calibration and validation specimens 11 Emission intensity measurements o f calibration specimens 13 Calculation of calibration equations 13 Validation using reference materials 13 8.7.1 General 13 8.7.2 Checking analytical accuracy using bulk re ference materials 13 © ISO 2017 – All rights reserved iii ISO 16962:2017(E) 14 14 Analysis of test specimens 15 9.1 Adjusting discharge parameters 15 9.2 Setting of measuring time and data acquisition rate 15 15 f f Expression of results 15 f 15 10.2 Determination of total coating mass per unit area (coating aeric mass) 17 10.2.1 General method 17 10.2.2 Method for special applications 17 10.3 Determination of average mass fractions 17 Precision 17 Test report 18 C hecking analytical accuracy us ing s ur face layer re ference materials 8.7.3 10 11 12 8.8 Verificatio n and dri ft co rrectio n 9.3 Quanti ying dep th p ro files o 0.1 E xp res s io n o Annex A tes t s p ecimens quantitative dep th p ro file (normative) Calculation of calibration constants and quantitative evaluation of 19 Annex B (informative) Suggestions concerning suitable spectral lines 31 Annex C (informative) Determination of coating mass per unit area (coating areic mass) 32 Annex D (informative) Additional information on international cooperative tests 38 Bibliography 40 d iv e p t h p r o f i l e s © ISO 2017 – All rights reserved ISO 16962:2017(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work o f 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 o f electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso org/directives) Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights ISO shall not be held responsible for identi fying any or all such patent rights Details o f any patent rights identified during the development o f the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso org/patents) Any trade name used in this document is in formation given for the convenience o f users and does not constitute an endorsement For an explanation on the voluntary nature o f standards, the meaning o f ISO specific terms and expressions related to formity assessment, as well as in formation about ISO’s adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso org/iso/foreword html This document was prepared by Technical Committee ISO/TC 201, Surface chemical analysis, Subcommittee SC 8, Glow discharge spectroscopy This second edition cancels and replaces the first edition (ISO 16962:2005), which has been technically revised © ISO 2017 – All rights reserved v ISO 16962:2017(E) Introduction T h i s c u ment i s a revi s ion o f I S O 169 62 D evelopments i n b o th GD - OE S i n s tru mentation and the typ e s o f z i nc- and/or a lu m i n iu m-b a s e d me ta l l ic co ati ngs c u rrently pro duce d have rendere d I S O 169 62 p a r tly obsolete, and this revision is intended to bring it up to date vi © ISO 2017 – All rights reserved INTERNATIONAL STANDARD ISO 16962:2017(E) Surface chemical analysis — Analysis of zinc- and/or aluminium-based metallic coatings by glow-discharge optical-emission spectrometry Scope T h i s c u ment s p e c i fie s a glow- d i s charge op tic a l- em i s s ion s p e c trome tric me tho d for the de term i nation of the thickness, mass per unit area and chemical composition of metallic surface coatings consisting of z i nc- and/or a lu m i n ium-b a s e d materi a l s T he a l loyi ng elements s idere d are n ickel, i ron, s i l icon, le ad and anti mony This method is applicable to zinc contents between 0,01 mass % and 100 mass %; aluminium contents between 0,01 mass % and 100 mass %; nickel contents between 0,01 mass % and 20 mass %; iron contents between 0,01 mass % and 20 mass %; silicon contents between 0,01 mass % and 15 mass %; magnesium contents between 0,01 mass% and 20 mass%; lead contents between 0,005 mass % and ma s s % , a nti mony contents b e twe en , 0 ma s s % a nd mas s % NO TE D ue to envi ro n menta l a nd he a lth r i s ks , le ad a nd a nti mo ny a re avoide d nowad ays , but th i s c u ment is also applicable to older products including these elements T he Normative references fol lowi ng c u ments are re ferre d to i n the tex t i n s uch a way th at s ome or a l l o f thei r content s titute s re qu i rements o f th i s c u ment For date d re ference s , on ly the e d ition cite d appl ie s For u ndate d re ference s , the late s t e d ition o f the re ference d c ument (i nclud i ng a ny amend ments) appl ie s ISO 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical composition ISO 17925 , Zinc and/or aluminium based coatings on steel — Determination of coating mass per unit area and chemical composition — Gravimetry, inductively coupled plasma atomic emission spectrometry and flame atomic absorption spectrometry Terms and definitions No term s and defi nition s a re l i s te d i n th i s c u ment ISO and IEC maintain terminological databases for use in standardization at the following addresses: — IEC Electropedia: available at http://www.electropedia org/ — ISO Online browsing platform: available at http://www.iso org/obp Principle T he a na lytic a l me tho d de s crib e d here i nvolve s the a) fol lowi ng pro ce s s e s: prep a ration o f the s ample to b e ana lys e d , genera l ly i n the form o f a flat plate or d i s c o f d i men s ion s appropriate to the i n s tr u ment or a na lytic a l re qu i rement (rou nd or re c tangu lar s ample s with a width o f more th an m m, genera l ly m m to 10 m m, a re s u itable) ; b) c atho d ic s putteri ng o f the s ur face co ati ng i n a d i re c t c urrent or rad io device; © ISO 2017 – All rights reserved fre quenc y glow- d i s charge ISO 16962:2017(E) c) excitation o f the analyte atoms in the plasma formed in the glow-discharge device; d) spectrometric measurement of the intensities of characteristic emission spectral lines of the analyte atoms and ions as a function o f sputtering time (qualitative depth profile); e) conversion o f the depth profile in units o f intensity versus time to mass fraction versus depth by means o f calibration functions (quantification) Calibration o f the system is achieved by measurements on calibration samples of known chemical composition and measured sputtering rate Apparatus 5.1 Glow-discharge optical-emission spectrometer 5.1.1 General The required instrumentation includes an optical-emission spectrometer system consisting o f a Grimm type[1] or similar glow-discharge source (direct current or radio frequency powered) and a simultaneous optical spectrometer as described in ISO 14707, capable of providing suitable spectral lines for the analyte elements It is also common to combine this with a sequential spectrometer (monochromator), allowing the addition o f an extra spectral channel to a depth profile measurement An array-type detector, such as a charge coupled device (CCD) or a charge injection device (CID) can also be used for simultaneous detection to cover a wide spectral range o f the analytical lines The inner diameter of the hollow anode of the glow-discharge source should be in the range mm to mm A cooling device for thin specimens, such as a metal block with circulating cooling liquid, is also recommended, but not strictly necessary for implementation o f the method Since the principle of determination is based on continuous sputtering of the surface layer, the spectrometer shall be equipped with a digital readout system for time-resolved measurement o f the emission intensities A system capable o f a data acquisition speed o f at least 300 measurements/second per spectral channel is recommended, but for a large number of applications speeds of > 50 measurements/second per spectral channel are acceptable In practice, it has been established that 10 to 100 measurements/second per spectral channel are suitable 5.1.2 Selection of spectral lines For each analyte to be determined, there exist a number o f spectral lines which can be used Suitable lines shall be selected on the basis of several factors, including the spectral range of the spectrometer used, the analyte mass fraction range, the sensitivity o f the spectral lines and any spectral inter ference rom other elements present in the test specimens For applications where several o f the analytes f of interest are major elements in the specimens, special attention shall be paid to the occurrence of sel f-absorption o f certain highly sensitive spectral lines (so-called “resonance lines”) Sel f-absorption causes non-linear calibration curves at high analyte mass fraction levels, and strongly sel f-absorbed lines should therefore be avoided for the determination of major elements Suggestions concerning suitable spectral lines are given in Annex B Spectral lines other than those listed may be used, so long as they have favourable characteristics 5.1.3 5.1.3.1 Selection of glow-discharge source type Anode size Most GD-OES instruments on the market are delivered with options to use various anode diameters, mm, mm and mm being the most common Some older instruments have one anode only, usually mm, while the most commonly used anode in modern instruments is mm A larger anode requires larger specimens and higher power during analysis; there fore, the specimen is heated to a greater extent On the other hand, a larger anode gives rise to a plasma of larger volume that emits more light, resulting in lower detection limits (i.e higher analytical sensitivity) Furthermore, a larger anode helps © ISO 2017 – All rights reserved ISO 16962:2017(E) to mask inhomogeneity within a sur face layer This may or may not be an advantage, depending on the application In a large number of applications, the mm anode is a good compromise However, in sur face analysis applications, it is rather common to encounter problems o f overheating o f the specimens due to sur face layers o f poor heat conductivity and/or very thin specimens, for example In such cases, a smaller anode (typically or 2,5 mm) is pre ferable, even i f there is some loss o f analytical sensitivity 5.1.3.2 Type of power supply The glow-discharge source can be either a type powered by a direct current (DC) power supply or a radio frequency (RF) type The most important di fference is that the RF type can sputter both conductive and non-conductive specimens; hence, this is the only type that can be used for polymer coatings and insulating oxide layers, for example On the other hand, it is technically simpler to measure and control the electrical source parameters (voltage, current, power) o f a DC type Several commercially available GD-OES systems can be delivered with the option to switch between DC and RF operation, but RF-only systems are becoming increasingly common In short, there are a very large number o f applications where DC or RF sources can be used and several where only an RF source can be used 5.1.3.3 Mode of operation Both DC and RF sources can be operated in several different modes with respect to the control of the electrical parameters (current, voltage, power) and the pressure There are several reasons for this: — “historical” reasons (older instruments have simpler but functional power supplies, while the technology has evolved, so newer models have more precise and easier-to-operate source control); — different manufacturers have chosen different solutions for source control; — there are some application-related issues where a particular mode of operation is to be preferred This document gives instructions for optimizing the source parameters based on several available modes of operation The most important reason for this is to make these instructions comprehensive so as to include several types o f instruments In most applications, there is no major di fference between these modes in terms o f analytical per formance, but there are other di fferences in terms o f practicality and ease o f operation For instance, a system equipped with active pressure regulation will automatically be adjusted to the same electrical source parameters every time a particular analytical method is used Without this technology, some manual adjustment o f the pressure to achieve the desired electrical source parameters is normally required NOTE In this context, what is known as the emission yield[2][3][4][7] forms the basis for calibration and quantification as described in this document The emission yield has been found to vary with the current, the voltage and, to a lesser extent, the pressure[4][7] It is impossible in practice to maintain all three parameters constant for all test specimens, due to variations in the electrical characteristics of different materials In several instrument types, the electrical source parameters (the plasma impedance) can there fore be maintained constant by means o f automatic systems that vary the pressure during analysis Alternatively, there exist methods to correct for impedance variations by means o f empirically derived functions [4][7] , and this type o f correction is implemented in the so ftware o f commercially available GD-OES systems 6.1 Adjusting the glow-discharge spectrometer system settings General Follow the manu facturer’s instructions or locally documented procedures for preparing the instrument for use For the optical system, the most important preparation step is to check that the entrance slit to the spectrometer is correctly adjusted, following the procedure given by the instrument manu facturer This ensures that the emission intensities are measured on the peaks of the spectral lines for optimum signal-to-background ratio and good reproducibility For further in formation, see ISO 14707 © ISO 2017 – All rights reserved ISO 16962:2017(E) The most important step in developing a method for a particular application is to optimize the parameters of the glow-discharge source The source parameters shall be chosen to achieve three aims: a) adequate sputtering o f the test specimen, to reduce the analysis time without overheating the specimen; b) good crater shape, for good depth resolution; c) constant excitation conditions in calibration and analysis, for optimum accuracy Trade-o ffs are o ften necessary among the three specified aims More detailed instructions on how to adjust the source parameters are given in 6.2 and 6.3 The settings of the high voltage for the detectors depend on the source parameters, but the procedure is the same for all modes o f operation o f the source This procedure is there fore only described for the first mode o f operation Similarly, the steps to adjust and optimize the source settings in terms o f signal stability and sputter crater shape are also similar in principle for all modes of operation Therefore, these procedures are only described in detail for the first mode o f operation NOTE There is no difference between DC and RF concerning the possibilities to measure the pressure However, there are large pressures di fferentials in a Grimm type source, and pressure readings obtained depend on the location of the pressure gauge Some instrument models have a pressure gauge attached to measure the actual pressure in the plasma, while others have a pressure gauge located on a “low pressure” side o f the source closer to the pump Therefore, the pressure readings can, for several instruments, just be used to adjust the source parameters of that particular instrument, not as a measure of the actual operating pressure in the plasma 6.2 Setting the parameters of a DC source 6.2.1 6.2.1.1 Constant applied current and voltage General The two control parameters are the applied current and the applied voltage Set the power supply for the glow-discharge source to constant current/constant voltage operation (current set by the power supply, voltage adjusted by pressure/gas flow regulation) Then, set the current and voltage to the typical values recommended by the manu facturer Alternatively, set the power supply to constant voltage/constant current operation (voltage set by the power supply, current adjusted by pressure/gas flow regulation) I f no recommended values are available, set the voltage to 700 V and the current to a value in the range mA to 10 mA for a mm or 2,5 mm anode, 15 mA to 30 mA for a mm anode or 40 mA to 100 mA for a mm or mm anode If no previous knowledge of the optimum current is available, it is recommended to start with a value somewhere in the middle of the recommended range NOTE For the purposes of this document, there is no difference between the two alternative modes of 6.2.1.2 Setting the high voltage of the detectors operation described above However, for applications to very thin films, there may be a small di fference in the very short start-up o f the discharge, a ffecting the analytical results to some extent Select test specimens with sur face layers o f all types to be determined For all test specimens, run the source while observing the output signals from the detectors for the analyte atoms Adjust the high voltage o f the photomultiplier (PMT) detectors in such a way that su fficient sensitivity is ensured at the lowest analyte mass fraction without saturation o f the detector system at the highest analyte mass fraction For array type detectors (CCD or CID), adjust the integration time in the same way as the high voltage for PMT © ISO 2017 – All rights reserved ISO 16962:2017(E) A.7.3 Calculation based on the mass fractions of the elements If a calibration function based on Formula (A.2) calculation steps was used for c a l ibration, c arr y out the fol lowi ng Provided that the s um o f all the elements determined cons titutes >9 % o f the material analysed, the mas s fraction, wi w i Dj D , of element i in segment j = j kiλ NOTE Formula (A.23): ( kiλ × Iiλ − B λrel ) j × 100 k × I − B ( ) ∑ iλ iλ λrel j i where o f s p ecimen D, expres sed in per cent, is given by is equal to R iλ (A.23) × ( ref/ D) q q Formula (A.23) incorporates a normalization of the sum of all the mass fractions to 100 % If non-linear calibration curves are used, replace the linear functions shown in Formula (A.23) corresponding non-linear functions For each segment, f f using Formula (A.24): j, o the dep th pro fi le o s p e c i men D, c a lc u l ate the s putteri ng rate p er u nit are a, q q Dj = q ref × ∑ ( kiλ × I iλ − B λ rel ) / 100 D, j (A.24) i For each segment, sputtered mass per unit area, by the j, and corre s p ond i ng ti me i nc rement, Δ tj, o f the dep th pro fi le o f s p e ci men D, the m mi D , of element i j Formula (A.25): (A.25) D j = q D j × w i D j × ∆t j / 100 i The total sputtered mass per unit area, m i s given b y tot = j ∑ m i mj tot, in segment j i s given b y Formula (A.26): (A.26) Dj i A.8 Calculation of mass fractions and sputtered mass using absolute sputtering rates A.8.1 General The calculation of elemental mass fractions and sputtered mass can proceed in accordance with various different sets of algorithms described below, depending on the calibration function used The fi na l re s u lts a re e qu iva lent, however A.8.2 Calculation based on elemental sputtering rate If a calibration function based on Formula (A.8) calculation steps For each segment, f f D × D′ for each element, j, o qua ntity 28 w i q j the dep th pro fi le o wa s used for c a l ibration, c a rr y out the s p e c i men D, c a lc u late from the ca l ibration fol lowi ng fu nc tion the i T h i s quantity i s the elementa l s putteri ng rate © ISO 2017 – All rights reserved ISO 16962:2017(E) P rovide d th at the s u m o f a l l the elements de term i ne d s titute s > % o f the materia l ana lys e d, calculate the sputtering rate, q ∑ D′ j = w i i D × q D′ j q D′ j , of segment j o f the dep th pro fi le o f s p e ci men D u s i ng D = w D × q D′ i j q i j (A.27) 100 The mass fraction, wiD j, of element i in segment j w Formula (A.27): D′ o f s p e ci men D i s given b y Formula (A.28): (A.28) j where wiD j is expressed in per cent The total sputtered mass per unit area, m jtot, in segment j Formula (A.29): a nd i n the corre s p ond i ng ti me i ncrement, Δ tj, i s given by m tot = q D′ j × ∆t j A j (A.29) D where AD is the area of the crater on specimen D A.8.3 Calculation based on mass fractions of the elements If a calibration function based on Formula (A.9) calculation steps wa s used for c a l ibration, c a rr y out the fol lowi ng P rovide d th at the s u m o f a l l the elements de term i ne d s titute s > % o f the materia l ana lys e d, calculate the mass fraction, wiD j, of element i in segment j of specimen D, expressed as a mass fraction in per cent, using Formula (A.30): w i Dj where k NOTE ( ki′λ × Iiλ − B λ′ ) j × 100 ′ ′ × − k I B ( ) ∑ iλ iλ λ j = ′λ i i is equal to R ′λ i q D′ (A.30) Formula (A.30) incorporates a normalization of the sum of all the mass fractions to 100 % If non-linear calibration curves are used, replace the linear functions shown in Formula (A.30) corresponding non-linear functions For each segment, j f D′ , using Formula (A.31): , o q D′ j = the dep th pro fi le, c a lc u l ate the s putteri ng rate, q i , and corres p ond i ng ti me i ncrement, Δ i s given b y m i Formula (A.32): j tj, = ∑ m i D j / A D (A.31) o f the dep th pro fi le, the s puttere d ma s s , (A.32) D j = q D′ j × w i D j × ∆t j / 100 The total sputtered mass per unit area, m j, in segment j m j ∑ ( ki′λ × Iiλ − B λ′ ) / 100 For each segment, j m iD j, of element i b y the i s given b y Formula (A.33): (A.33) i © ISO 2017 – All rights reserved 29 ISO 16962:2017(E) A.9 Calculation of sputtered depth A.9.1 General T he ana lytic a l me tho d de s c rib e d i n th i s c ument de term i ne s the s puttere d ma s s and mas s frac tion s o f e ach element To de term i ne the s puttere d dep th , the den s ity o f the s puttere d materia l s to b e known For the materials considered here, it can be estimated from the elemental composition and the densities of the pure elements There are two existing methods for calculating the sputtered depth, either of which can be utilized for the pur p o s e s o f th i s a na lytic a l me tho d A.9.2 Calculation based on constant atomic volume For each segment, j , o f the dep th pro fi le o f s p e c i men D, c a lc u late the den s ity, ρ = 100 / j ∑ w i ρ i where ρi For each segment, j Dj (A.34) i i s the den s ity o f the pure element i , o f the dep th pro fi le, c a lc u late the th ickne s s , z j = m , using Formula (A.34): ρj zj, of that segment using Formula (A.35): (A.35) tot j ρ × AD j zj over j using Formula (A.35) it is interesting to also calculate the sputtering rate per unit area in segment j T he to ta l dep th i s de term i ne d b y s u m m i ng T hough no t s tric tly ne ce s s ar y, b y d i vid i ng m jtot b y Δ tj A.9.3 Calculation based on averaged density For each segment, j f i, using Formula (A.36): , o the dep th pro fi le o f s p e c i men D, c a lc u late the atom ic w / W i Dj i A = ij w / W i Dj i i where Wi is the atomic mass of element i frac tion, A ij, of each element, (A.36) ∑ For each segment, j , o f the dep th pro fi le , c a lc u late the e s ti mate d den s ity, ρ = j ∑ A ij × ρi i For each segment, j zj, using Formula zj over the range of values of j that are of interest , o f the dep th pro fi le, c a lc u l ate the th ickne s s , dep th i s de term i ne d by s u m m i ng 30 , using Formula (A.37): (A.37) ρj (A.35) The total © ISO 2017 – All rights reserved ISO 16962:2017(E) Annex B (informative) Suggestions concerning suitable spectral lines Table B.1 — Suggested spectral lines for determination of given elements Element a Zn Zn Zn Al Al Ni Ni Ni Si Si Si Fe Fe Fe Fe Fe Cu Cu Mg Use non-linear calibration curve © ISO 2017 – All rights reserved Wavelength (nm) 330,26 334,50 481,053 172,50 396,15 231,603 341,78 349,30 212,41 251,61 288,16 249,318 259,94 271,44 371,94 379,50 296,12 327,40 383,83 Estimated useful mass fraction range in % 0,001 to 100 0,001 to 100 0,001 to 100 0,1 to 100 0,001 to 100 a 0,01 to 100 0,001 to 100 a 0,005 to 100 a Not determined Not determined 0,001 to 20 0,01 to 100 0,01 to 100 0,1 to 100 0,005 to 100 a 0,01 to 100 0,01 to 100 0,001 to a 0,001 to 100 Comments Self-absorption Weak self-absorption Weak self-absorption Weak self-absorption Strong self-absorption 31 ISO 16962:2017(E) Annex C (informative) Determination of coating mass per unit area (coating areic mass) C.1 General Calculation o f the coating areic mass for a particular element can proceed by integrating the area under the depth profile for that element within the depth (or time) domain taken to represent the coating, an option available in the software of all commercial GD-OES instruments How this integration is carried out can be understood from the quantitative depth profile expressed in ordinate units o f g/m2/s and abscissa units of sec, available as an option for graphical presentation in the software of some commercial GD-OES instruments, see Figure C.1 The integrated areic mass of a specific element is obtained by summing the contributions from each time (depth) segment within the domain taken to represent the coating Calculation o f the total areic mass o f a coating can then be accomplished by summing the coating areic masses for the individual elements A key issue in these calculations is the determination o f the domain that represents the coating This is particularly true when a given element is present at significant mass fractions in both the coating and the substrate, e.g a ZnFe coating on a steel substrate or an AlSi coating on an aluminium substrate Due to the limited depth resolution it is impossible to directly separate the contributions from the coating and substrate respectively in the inter face region from the elemental depth profile o f that element It is there fore necessary to make an indirect determination based on the depth profile o f another major element in the coating For such cases, the following two methods are recommended C.2 Method First, consider an element that is present at a higher mass fraction in the substrate than in the coating The approach for such an element is most easily explained by means o f the galvanneal (ZnFe) coating example in Figure C.1 (see also Figure in the main text) In this example, Fe is the element of interest Time tt or the corresponding depth dd (when Fe in the base metal begins to appear) is defined as the time (or depth) at which the ordinate value for the major element in the coating (Zn in this case) falls to 95 % of its maximum or plateau-edge value The time tt or depth dd can be determined from any of the three graphical presentations o f the depth profile in Figure C.1 After time tt, the Fe in the coating is assumed to decrease and reach zero in relation to the Zn profile, i.e the Fe mass fraction o f the coating material remains constant after time tt (beyond depth dd) Therefore, the Fe areic mass within the transition zone is equal to the Zn areic mass between dd and the integration end point L , multiplied by an adjustment factor equal to the ratio o f the Fe to Zn ordinate values at dd (tt) The integration end point at depth D is defined as the Zn 50 % point plus three times the di fference between depth dd and the Zn 50 % point At point D, the remaining Zn under the depth profile is assumed to be negligible The total Fe areic mass is then the sum of the Fe areic mass within the transition zone and the Fe areic mass from time zero to tt; see Figure C.2 An alternative definition o f tt or dd is possible, whenever there are monitored elements that are absent in the coating, but present in the substrate In such a case, tt may be defined as the time at which those elements NOTE are first detected Nb, Mo, Mn, Cu and Co are examples o f possible monitored elements 32 © ISO 2017 – All rights reserved ISO 16962:2017(E) In the case of coating elements that are present at higher mass fractions in the coating than in the substrate, the coating mass per unit area is taken to be the integral from time zero to the integration end point L Key X time (s) Y elemental aeric sputtering rate (g/s/m2 ) t 95 % of maximum Zn sputtering rate t © ISO 2017 – All rights reserved 33 ISO 16962:2017(E) Key X time (s) Y elemental mass fraction (%) tt 95 % of Zn coating plateau value Key X depth (µm) Y elemental mass fraction (%) dd 95% of Zn coating plateau value D integration end point for Zn F i g u r e C — Q u a n t i t a t i v e d e p t h p r o f i l e s f o r d e t e r m i n a t i o n o f t h value in a ZnFe galvanneal coating 34 e % p o i n t o f t h e Z n p l a t e a u © ISO 2017 – All rights reserved ISO 16962:2017(E) Key X depth (µm) Y elemental mass fraction (%) F i g u r e C — Q u a n t i t a p t i r v e o f i d l e e i p n t h t h p e r i o f i n t l e e r s f o a c f e a g d a e t l v e r a n m n i e n a e l d Z b n y F e m c e t o a h t o i d n g , w i t h t h e F e c o a t i n g C.2.1 Adjusting the Fe calibration In order to obtain good agreement with wet chemical reference methods (in the case of ZnFe ISO 17925) within statistical limits, it is normally necessary to adjust the Fe calibration o f the GD-OES method by the use of coated ZnFe RM’s There can be several reasons for discrepancies between GD-OES and wet chemical methods, the most likely are the following a) A slight di fference between the Fe emission yield in the ZnFe and steels,since steels are normally used to calibrate for high Fe mass fractions (see 8.4) b) The Fe mass fraction in the coating beyond depth dd increases due to the presence of FeZn phases with higher Fe content, leading to an underestimation of the Fe areic mass in the range dd to L In order to compensate for any discrepancies between GD-OES and re ference methods, the following procedure is recommended a) Set up an appropriate GD-OES analytical method and calibrate according to calibration samples Clause 8, using bulk b) Analyse a few coated ZnFe RM’s as unkowns, and apply method to determine the Fe mass fraction in the coatings c) Calculate the ratio Fe (wet chemical)/Fe (GD-OES) for all ZnFe RM’s; then, calculate the average ratio d) Multiply the slope o f the Fe calibration function with the average ratio from step How this change can be accomplished in an analytical method depends on the so ftware o f the particular instrument used, more detailed instructions can therefore not be given here e) Repeat step with the adjusted Fe calibration Veri fy that satis factory agreement with the wet chemical data is obtained I f this is not the case, repeat steps to until satis factory agreement is achieved © ISO 2017 – All rights reserved 35 ISO 16962:2017(E) C.3 Method T h i s pro ce du re i s b as e d up on the comp o s itiona l dep th pro fi le expre s s e d i n ord i nate u nits o f mas s fraction and abscissa units of depth As in method 1, a galvanneal (ZnFe) coating is used as an example Figure C.3 f T he ol lowi ng p o s ition s i n the qua nti fie d dep th pro fi le are defi ne d; s e e Key X Y W S L dep th (μm) analyte mas s fractio n (% ) interface width depth at which mass fractions of Zn and Fe are equal depth corresponding to S plus W Figure C.3 — Quantitative depth profile expressed as mass fraction vs depth, illustrating method for a ZnFe galvanneal coating T he fi rs t s tep i s to fi nd the dep th s at wh ich the Z n ma s s ma s s frac tion frac tion fa l l s to % and 16 % o f the p late au Z n i n the co ati ng D e s ignate the s e dep th s a s Z n % and Z n 16 % , re s p e c ti vely — D efi ne the i nter face width — D efi ne dep th — D efi ne dep th W as the difference between Zn 16 % and Zn 84 % S as the depth at which the mass fractions of Zn and Fe are equal L as depth S plus the interface width W — Calculate the (total) areic mass Fe 0- S of Fe from depth zero to depth S — Calculate the areic mass Zn S- L of Zn from depth S to depth L B as e d on the s ym me tr y o f the dep th pro fi le s o f Z n and Fe, the Fe a reic ma s s o f the s ub s trate up to the depth S S expressed as Fe0– S × Zn The Fe areic mass from S to L S- L assumed to be proportional to Zn S-L S– L × Zn S- L combining these expressions, the total Fe areic mass of the coating Fe 0-L (coating) is calculated according to Formula (C.1): Fe0-L (coating) = Fe 0- S (C.1) S- L i s a s s ume d to b e prop or tiona l to the Z n areic ma s s b eyond the dep th (s ub s trate) = α , mathematic a l ly i n the co ati ng i s s i m i larly ; mathematic a l ly expre s s e d as Fe (co ati ng) = α By (to ta l) – α × Z n Where α i s an adj u s tment fac tor wh ich has to b e empi ric a l ly de term i ne d co ati ngs with a n average Fe mas s 36 frac tion clo s e to 10 % , it h as b e en for fou nd e ach appl ic ation For Z nFe that α = , give s re s u lts © ISO 2017 – All rights reserved ISO 16962:2017(E) i n go o d agre ement with we t chem ic a l re ference me tho d s H owever, the corre c t va lue dep end s on s evera l fac tors © ISO 2017 – All rights reserved for α varie s a nd e g i n s tru ment typ e, glow- d i s cha rge s ou rce p arame ters and co ati ng typ e 37 ISO 16962:2017(E) Annex D (informative) Additional information on international cooperative tests Table and Table f f and 2002 on zinc and/or aluminium-base coating samples in three countries involving four laboratories The results of the trials were reported in document ISO/TC 201/SC N 38 revised (see in Annex E) and N 55 (see in Annex E) The test samples used and results for coating areic mass and element contents obtained in international cooperative tests are listed in Table D.1 The precision data are presented in graphical form in Figure D.1 and Figure D.2 were derive d rom the re s u lts o i nternationa l a na lytic a l tria l s c arrie d out i n 01 T hey i nclude data on bu l k s ample s a nd re s u lts o f i nter-lab orator y te s ts c arrie d out at E C I S S/ TC Table D.1 — Test sample used and their found values Samples No 101 102 103 104 12 201 202 203 204 38 Kinds of coating Zn-Fe(Hot dip coating and annealing; Galvanneal) Zn-Fe(Hot dip coating and annealing; Galvanneal) Zn-Fe(Hot dip coating and annealing; Galvanneal) Zn-Fe(Hot dip coating and annealing; Galvanneal) Zn-Fe(Hot dip coating and annealing; Galvanneal) Al-Zn (Hot dip coating) Z n-Ni( E le c trol y tic co ati ng) Zn(Hot dip coating) Z n-Ni( E le c trol y tic co ati ng) Zn(Hot dip coating; Galfan) Al-Zn(Hot dip coating; Aluzinc) Coating areic mass Chemical composition (mass %) g/m 57 Zn Fe Al 89,1 10,23 0,210 49,0 88,3 11,3 0,37 50,7 89,5 10,05 0,38 49,7 90,6 9,0 0,39 53,3 86,6 13,03 0,37 91,4 17,81 113 44 110 81 42,6 86,2 99,5 86,7 94,9 45,4 54,9 0,35 5,1 53,2 Ni 12,5 Si Pb 1,29 0,11 13,2 1,9 © ISO 2017 – All rights reserved ISO 16962:2017(E) Key X coating areic mass (g/m2 ) Y rep eatab ility s tandard deviatio n (S D r) (g/m 2) Figure D.1 — Relationship between coating areic mass and repeatability standard deviation (SD r) Key X element content (mass %) Y rep eatab ility s tandard deviatio n (S D r) (mas s % ) Figure D.2 — Logarithmic relationship between element contents and repeatability standard deviation © ISO 2017 – All rights reserved 39 ISO 16962:2017(E) Bibliography [1] [2] [3] Grimm , W., Spectrochim Acta Part B, 23 (1968), p 443 Takadoum , J., P irrin , Anal , (1984), p 174 J.C., Pons C orbeau, J., B erneron, R., and C harbonnier, J.C., Surf Interf Takimoto , K., N ishizaka , K., S uzuki , K., and O htsubo , T., Nippon Steel Technical Report 33 , (1987) p 28 [4] B engtson, A., E klund, A., and S aric , A., J Anal At Spectrom , (1991), p 563 [5] N aoumidis , A., Guntur, D., M azurkiewicz , M., Nickel , H., and F ischer, W., Proceedings of 3rd User-Meeting “Analytical Glow Discharge Spectroscopy”, p 138, Jülich (1990) [6] Payling, R., Spectroscopy, 13 (1998), p 36 [7] B engtson, A., and Nelis , T., Anal Bioanal Chem , 385 (2006), p 568 [8] Wilken, L, H off mann, V., Wetzig, K., Spectrochim Acta B, 62 (2007) p 1085–1122 [9] M arshall , K.A., C asper, T.J., B rushwyler, K.R., M itchell , J.C., J Anal At Spectrom , 18 (2003) p 637–645 [10] Wilken, L, H off mann, V., Wetzig, K., J Anal At Spectrom., 18 (2003), p 1141–1145 [11] M artin, A., M artinez , A., P ereiro , R., B ordel , N and S anz-M edel , A , Spectrochim Acta B, 62 (2007), p 1263 1268 [12] ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results — Part 1: General principles and definitions [13] ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination ofrepeatability and reproducibility ofa standard measurement method [14] ISO 5725-6, Accuracy (trueness and precision) of measurement methods and results — Part 6: Use in practice of accuracy values [15] ISO 9000:2015, Quality management systems — Fundamentals and vocabulary [16] ISO 11505, Surface chemical analysis — General procedures for quantitative compositional depth profiling by glow discharge optical emission spectrometry [17] ISO 14707, Surface chemical analysis — Glow discharge optical emission spectrometry (GD-OES) — Introduction to use [18] ISO/IEC 17025:2005, laboratories General requirements for the competence of testing and calibration [19] ISO 18115-1, Surface chemical analysis — Vocabulary — Part 1: General terms and terms used in spectroscopy [20] ISO/TS 25138, Surface chemical analysis — Analysis of metal oxide films by glow-discharge opticalemission spectrometry 40 © ISO 2017 – All rights reserved ISO 16962:2017(E) I CS 40 40 Price based on 40 pages © ISO 2017 – All rights reserved