SIST EN 10318:2005
(Main)Determination of thickness and chemical composition of zinc- and aluminium-based metallic coatings - Routine method
Determination of thickness and chemical composition of zinc- and aluminium-based metallic coatings - Routine method
This document specifies a glow discharge optical emission spectrometric method for the determination of the thickness and chemical composition of metallic surface coatings consisting of zinc and aluminium based alloys. The alloying elements considered are aluminium, nickel, silicon and lead.
This method is applicable to zinc contents between 40 % (m/m) and 100 % (m/m); aluminium contents between 0,01 % (m/m) and 60 % (m/m); nickel contents between 0,01 % (m/m) and 15 % (m/m); silicon contents between 0,01 % (m/m) and 3 % (m/m); lead contents between 0,005 % (m/m) and 0,1 % (m/m).
Bestimmung der Dicke und der chemischen Zusammensetzung metallischer Überzüge auf Basis von Zink und Aluminium - Standard-Verfahren
Diese Europäische Norm legt ein Emissions-Spektralanalyseverfahren mittels Glimmentladung zur Bestimmung der Dicke und der chemischen Zusammensetzung metallischer Überzüge, die auf Zink- und Aluminiumlegierungen basieren, fest. Als Legierungselemente werden Aluminium, Nickel, Silicium und Blei berücksichtigt.
Dieses Verfahren ist anwendbar bei Zinkanteilen zwischen 40 % (m/m) und 100 % (m/m), Aluminiumanteilen zwischen 0,01 % (m/m) und 60 % (m/m), Nickelanteilen zwischen 0,01 % (m/m) und 15 % (m/m), Siliciumanteilen zwischen 0,01 % (m/m) und 3 % (m/m) und Bleianteilen zwischen 0,005 % (m/m) und 0,1 % (m/m).
Détermination de l'épaisseur et de la composition chimique des revetements en zinc et en alliage d'aluminium - Méthode de routine
La présente Norme européenne spécifie une méthode par spectrométrie d'émission optique avec décharge luminescente pour la détermination de l'épaisseur et de la composition chimique des revetements métalliques de surface en alliages de zinc et d'aluminium. Les éléments d'alliage pris en considération sont l'aluminium, le nickel, le fer, le silicium et le plomb.
La présente norme est applicable a des teneurs en zinc comprises entre 40 % (m/m) et 100 % (m/m) ; a des teneurs en aluminium comprises entre 0,01 % (m/m) et 60 % (m/m) ; a des teneurs en nickel comprises entre 0,01 % (m/m) et 15 % (m/m) ; a des teneurs en silicium comprises entre 0,01 % (m/m) et 3 % (m/m) ; a des teneurs en plomb comprises entre 0,005 % (m/m) et 0,1 % (m/m).
Ugotavljanje debeline in kemične sestave kovinskih prevlek na osnovi cinka in aluminija – Rutinska metoda
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 10318:2005
01-september-2005
8JRWDYOMDQMHGHEHOLQHLQNHPLþQHVHVWDYHNRYLQVNLKSUHYOHNQDRVQRYLFLQNDLQ
DOXPLQLMD±5XWLQVNDPHWRGD
Determination of thickness and chemical composition of zinc- and aluminium-based
metallic coatings - Routine method
Bestimmung der Dicke und der chemischen Zusammensetzung metallischer Überzüge
auf Basis von Zink und Aluminium - Standard-Verfahren
Détermination de l'épaisseur et de la composition chimique des revetements en zinc et
en alliage d'aluminium - Méthode de routine
Ta slovenski standard je istoveten z: EN 10318:2005
ICS:
17.040.20 Lastnosti površin Properties of surfaces
25.220.40 Kovinske prevleke Metallic coatings
SIST EN 10318:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 10318:2005
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SIST EN 10318:2005
EUROPEAN STANDARD
EN 10318
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2005
ICS 17.040.20; 25.220.40
English version
Determination of thickness and chemical composition of zinc-
and aluminium-based metallic coatings - Routine method
Détermination de l´épaisseur et de la composition chimique Bestimmung der Dicke und der chemischen
des revêtements en zinc et en alliage d´aluminium - Zusammensetzung metallischer Überzüge auf Basis von
Méthode de routine Zink und Aluminium - Standard-Verfahren
This European Standard was approved by CEN on 21 March 2005.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
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 STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 10318:2005: E
worldwide for CEN national Members.
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Contents
Page
Foreword .3
1 Scope .4
2 Normative references .4
3 Principle.4
4 Apparatus .4
4.1 Glow discharge optical emission spectrometer .4
4.2 Data acquisition .5
5 Sampling.5
6 Procedure .6
6.1 Selection of spectral lines.6
6.2 Optimising the glow discharge spectrometer settings .6
6.3 Calibration .8
7 Verification of the analytical accuracy .10
8 Expression of results.10
8.1 Method of calculation .10
8.2 Precision.11
9 Test report .17
Annex A (normative) Calculation of calibration constants and quantitative evaluation of depth
profiles.18
Bibliography.23
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Foreword
This European Standard (EN 10318:2005) has been prepared by Technical Committee ECISS/TC 20 “Methods of
chemical analysis of ferrous products”, the secretariat of which is held by SIS.
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 November 2005, and conflicting national standards shall be withdrawn at the latest
by November 2005.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: 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.
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1 Scope
This European Standard specifies a glow discharge optical emission spectrometric method for the determination of
the thickness and chemical composition of metallic surface coatings consisting of zinc and aluminium based alloys.
The alloying elements considered are aluminium, nickel, silicon and lead.
This method is applicable to zinc contents between 40 % (m/m) and 100 % (m/m); aluminium contents between
0,01 % (m/m) and 60 % (m/m); nickel contents between 0,01 % (m/m) and 15 % (m/m); silicon contents between
0,01 % (m/m) and 3 % (m/m); lead contents between 0,005 % (m/m) and 0,1 % (m/m).
2 Normative references
Not applicable.
3 Principle
The analytical method described here involves the following processes:
a) Cathodic sputtering of the surface coating in a direct current glow discharge device;
b) Optical excitation of the analyte atoms in the plasma formed in the glow discharge device;
c) Spectrometric measurement of characteristic emission spectral lines of the analyte atoms as a function of
sputtering time (depth profile); and
d) Conversion of the depth profile in units of intensity versus time to mass fraction versus depth by means of
calibration functions (quantification). Calibration of the system is achieved by measurements on calibration
samples of known chemical composition and measured sputtering rate.
4 Apparatus
4.1 Glow discharge optical emission spectrometer
4.1.1 General
An optical emission spectrometer equipped with a Grimm type (1) or similar direct current glow discharge source
and a simultaneous optical spectrometer, incorporating suitable spectral lines for the analyte elements (see Table 1
for recommended lines) shall be used.
The inner diameter of the hollow anode of the glow discharge shall be in the range 2 mm to 8 mm. A cooling device
for thin samples, such as a metal block with circulating cooling liquid, is also recommended, but not strictly
necessary for implementation of the method.
It is desirable for the instrument to conform to the performance specifications given in 4.1.2 and 4.1.3, to be
evaluated in 6.2.6.
4.1.2 Minimum repeatability
Perform 10 measurements of the emission intensity on a homogeneous bulk sample with a content of the analyte
exceeding 1 % (m/m). Allow the discharge at least 60 s stabilisation time (often referred to as preburn) before each
intensity measurement. Each measurement shall be located on a newly prepared surface of the sample. Calculate
the standard deviation of the 10 measurements. The standard deviation should not exceed 2 % of the mean
intensity of the analyte. If this is the case, repeat the test two more times. If the high standard deviation is
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repeatable, there is probably some malfunction in the instrument or the sample used is not homogeneous. Before
proceeding, the cause of the problem should be investigated and rectified.
4.1.3 Limit of detection
Detection limits are instrument-dependent and matrix-dependent. Consequently, the detection limit for a given
analyte cannot be uniquely determined for every available instrument or for the full range of Zn-based alloys
considered here. For the purposes of this document, the detection limit for each analyte will be acceptable if it is
equal to or less than one third of the lowest concentration to be determined in the intended applications. The
detection limit is determined using the method explained below.
a). Select a bulk sample to be used as a blank. The sample composition should be similar to the coatings to be
analyzed in terms of the elemental composition of the matrix. Further, it shall be known to contain less than
-1
0,1 mg kg of the analyte.
b). Perform ten replicate burns on the blank. For each burn, acquire the emission intensity at the analytical
wavelength for 10 s. These are the background emission intensity measurements. The glow discharge
conditions used should be the same as those that will be used in the analysis of the coated samples. For each
measurement, the blank should be preburned at these conditions for a sufficient length of time to achieve
stable signals prior to the quantification of the emission intensity. An unsputtered area of the surface of the
blank for each individual burn shall be used.
c). Compute the detection limit using the following equation:
3× S
DL =
m
where
DL is the detection limit;
S is the standard deviation of the ten background intensity measurements performed in step (2);
m is the analytical sensitivity derived from the instrument calibration expressed as the ratio of intensity to mass
fraction.
If the detection limit calculated is greater than one third of the lowest concentration to be determined in the
intended applications, then the test should be repeated. If the second value calculated is also greater than one third
of the lowest concentration to be determined in the intended applications, then there may be an instrument
malfunction. In such a case, the problem should be investigated prior to analyzing unknown samples.
4.2 Data acquisition
Since the principle of determination is based on continuous sputtering of the surface coating, the spectrometer shall
be equipped with a digital readout system for time-resolved measurement of the emission intensities. A system with
capability for data acquisition speed of at least 500 measurements/second per spectral channel is recommended,
but for the applications within the scope of this standard a speed of 2 measurements/second per spectral channel
may be acceptable.
5 Sampling
Carry out sampling in accordance with the recommendations of the manufacturer of the coated material. In general,
the edges of a coated strip should be avoided. The size of the test samples should be suitable for the glow
discharge source used. Typically, round or rectangular samples with a width of 20 mm to 100 mm are suitable.
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6 Procedure
6.1 Selection of spectral lines
For each analyte to be determined there exists a number of 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, analyte
concentration range, sensitivity of the spectral lines and spectral interference from other elements present in the
samples. In this type of application, where most of the analytes of interest are major elements in the samples,
special attention shall be paid to the occurrence of self-absorption of certain highly sensitive spectral lines. Self-
absorption may cause severe non-linearity of calibration curves at high analyte concentration levels, and such lines
should therefore be avoided for the determination of majors. In Table 1, some suggestions concerning suitable
spectral lines are given.
Table 1 — Suggested spectral lines for determination of given elements
Element Wavelength Estimated useful Comments
concentration range
(nm)
% (m/m)
Zn 330,26 0,001 to 100
Zn 334,50 0,001 to 100
Zn 481,053 0,001 to 100
Al 172,50 0,1 to 100
a
Al 396,15 Self-absorption
0,001 to 100
Ni 231,603 0,01 to 100
a
Ni 341,78 Weak self-absorption
0,001 to 100
a
Ni 349,30 0,005 to 100 Weak self-absorption
Pb 202,20 0,001 to 10
Pb 405,87 0,01 to 100
Si 212,41 No data available
Si 251,61 No data available
Si 288,16 0,001 to 20
Fe 249,318 0,01 to 100
Fe 259,94 0,01 to 100
Fe 271,44 0,1 to 100
a
Fe 371,94 Weak self-absorption
0,005 to 100
Fe 379,50 0,01 to 100
Cu 296,12 0,01 to 100
a
Cu 327,40 Strong self-absorption
0,001 to 5
a Use of non-linear calibration curve recommended.
6.2 Optimising the glow discharge spectrometer settings
6.2.1 General
Follow the manufacturer’s instructions for preparing the instrument for use. In particular, check that the entrance slit
to the spectrometer is correctly adjusted, following the procedure given by the instrument manufacturer. This
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ensures that the emission intensities are measured on the peaks of the spectral lines for optimal signal to
background ratio. For further information, see e.g. ISO 14707.
The source parameters shall be chosen to achieve three aims: adequate sputtering of the sample, to reduce the
analysis time without over-heating the coatings; good crater shape, for good depth resolution; and constant
excitation conditions in calibration and analysis, for optimum accuracy. There are often tradeoffs among the three
specified aims.
Modern DC glow discharge spectrometers usually have provisions for complete control/measurement of the
electrical parameters (current, voltage, power), allowing any two of these parameters to be locked to constant
values by varying the pressure (active pressure regulation). Older spectrometers often lack an active pressure
regulation system, but the pressure can still be adjusted manually to maintain nearly constant current and voltage
during calibration measurements.
6.2.2 Constant applied current and voltage
The two control parameters are applied current and voltage. Set the power supply for the glow discharge source to
constant current – constant voltage operation. First set the current and voltage to typical values recommended by
the manufacturer. If no recommended values are available, set the current to a value in the range 5 mA to 10 mA
for a 2 mm or 2,5 mm anode, 15 mA to 30 mA for a 4 mm anode, 40 mA to 100 mA for a 7 mm or 8 mm anode. If
no beforehand knowledge about the optimum current is at hand, it is recommended to start with a value
somewhere in the middle of the recommended range, and the voltage at 700 V.
Set the high voltage of the detectors as described in 6.2.4.
Adjust the discharge parameters as described in 6.2.5, adjusting first the current and if necessary the voltage.
6.2.3 Constant applied current and pressure
The two control parameters are applied current and pressure. Set the power supply for the glow discharge source
to constant current operation. First set the current to a typical value recommended by the manufacturer. If no
recommended values are available, set the current to a value in the range 5 mA to 10 mA for a 2 mm or 2,5 mm
anode, 15 mA to 30 mA for a 4 mm anode, 40 mA to 100 mA for a 7 mm or 8 mm anode. If no beforehand
knowledge about the optimum current is at hand, it is recommended to start with a value somewhere in the middle
of the recommended range. Sputter a typical coated test sample, and adjust the pressure until a voltage of approxi-
mately 600 V is attained in the coating.
Set the high voltage of the detectors as described in 6.2.4.
Adjust the discharge parameters as described in 6.2.5, adjusting first the current and if necessary the pressure.
Before sputtering a new sample type, make a test run in order to ensure that the voltage is not altered more than
5 % from the previously selected value. If this is the case, readjust the pressure until the correct value is attained.
These conditions are then used during analysis.
6.2.4 Setting the high voltage of the detectors
Select test samples with coatings of all types to be determined. Using these samples, run the source while
observing the output signals from the detectors for the analyte atoms. Adjust the high voltage of the detectors in
such a way that sufficient sensitivity at the lowest analyte concentrations is ensured, without saturation of the
detector system at the highest analyte concentrations.
6.2.5 Adjusting the discharge parameters
For each type of test sample carry out a full depth profile measurement, sputtering it in the glow discharge for a
sufficiently long time to remove the coating completely and continue well into the base material. By observing the
emission intensities as a function of sputtering time (often referred to as the qualitative depth profile), verify that the
selected source settings give stable emission signals throughout the depth profile and into the substrate. Unstable
emission signals may indicate thermal instability on the sample surface; sample cooling is beneficial in this regard.
If this is found not to be the case, reduce one of the control parameters by a small amount and sputter through the
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coatings again. If the stability is still unsatisfactory, reduce the other control parameter by a small amount and
repeat the measurements. If found necessary, repeat this procedure for a number of control parameter
combinations until stable emission conditions are obtained.
6.2.6 Preliminary precision test
Select a few suitable bulk calibration samples (see 6.3.3), and perform tests described in 4.1.2 and 4.1.3. Ensure
that the discharge parameters and detector high voltages are the same as those selected for the coated materials.
These tests are carried out to confirm that the operation procedure is adequate.
6.3 Calibration
6.3.1 General
Calibration of the system consists of determining, for each analyte and spectral line, a quantity known as the
emission yield (2,3,4), which is defined as the integrated emission intensity per unit mass of the analyte. The
principle of quantification used in this standard is based on the observation that the emission yield is a matrix-
independent quantity, or at least very nearly so (3,5). In order to determine the emission yield, it is necessary to
know both the chemical composition and the sputtering rates (mass loss rate) of the calibration samples.
It is not necessary to prepare a new calibration for each series of determinations of unknown samples. Instead,
only a limited number of the calibration samples are re-run in order to determine the instrumental drift in sensitivity
and background for each spectral channel used in the method. For each channel, a high and a low intensity point is
required. The measured intensities are then corrected for the drift prior to the calculation of the quantitative results.
This procedure, referred to as drift correction or recalibration, is routinely employed in both optical emission and X-
ray fluorescence spectrometry for bulk analysis.
6.3.2 Calibration samples
6.3.2.1 General
Whenever possible, spectrometric calibration samples issued as CRMs (Certified Reference Materials) should be
used. Due to the quantification being based on emission yields, the calibration samples need not be very similar to
the coating materials in composition, but shall have sputtering rates which are reproducible. In particular, pure or
nearly pure zinc samples are not recommended due to difficulties in obtaining reproducible and stable sputtering
rates in zinc. Furthermore, high purity metals are not necessary in order to calibrate correctly for high
concentrations, but they are valuable for the determination of the spectral backgrounds. The following
considerations are the most important in the selection of the calibration samples:
a) there shall be at least 5 calibration samples for each analyte, covering a range from zero to the highest
concentrations to be determined;
b) samples shall be homogeneous;
c) samples shall have well determined sputtering rates.
Based on these general recommendations, the following types of calibration samples are suggested in 6.3.2.2 to
6.3.2.7. It should be noted that these recommendations constitute a minimum requirement, and additional
calibration samples of other alloy types containing the analytes may be used.
6.3.2.2 Brass calibration samples
Select at least two brass samples with zinc contents of 25 % to 50 % (m/m); aluminium contents of 1 % to 4 %
(m/m); lead contents of 1 % to 4 % (m/m).
6.3.2.3 ZnAl alloy samples
Select at least two ZnAl alloy samples with a zinc content of 40 % to 95 % (m/m).
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6.3.2.4 Stainless steel samples
Select at least two stainless steels with nickel contents of 10 % to 40 % (m/m).
6.3.2.5 Nickel based alloy samples
Select at least one nickel based alloy sample with a nickel content of more than 70 % (m/m).
6.3.2.6 Aluminium - silicon alloy samples
Select at least one aluminium-silicon alloy sample with a silicon content of 5 % to 10 % (m/m).
6.3.2.7 High purity copper sample
Select a high purity copper sample with concentrations of the analytes less than 0,001 % (m/m). This sample can
be used as zero points for all analytes except copper, even if the exact concentrations of the analytes are not
known.
6.3.3 Determination of the sputtering rate of calibration samples
The term sputtering rate is understood here to be equivalent to the mass loss rate during sputtering in the glow
discharge. In order to determine this quantity for the calibration samples, the following procedure is recommended:
a) prepare the sample surface according to recommendations from the instrument manufacturer;
b) adjust the glow discharge current and voltage to those selected in 6.2;
c) sputter the sample for a time estimated to result in a crater 20 µm to 40 µm deep, recording the total sputtering
time;
d) repeat c) several times if the sample surface area is sufficiently large, recording the total sputtering time for
each crater;
e) measure the average depth of each crater by means of an optical or mechanical profilometer device,
performing at least 4 profile traces in different directions across the centre of the crater;
f) calculate the sputtered volume of each crater, the sputtered mass as the volume multiplied by the density of
the sample;
g) calculate the sputtering rate for each crater as the mass loss divided by the total sputtering time;
h) calculate the average sputtering rate and the standard deviation from the measurements of each crater.
The profilometer should have an accuracy in the depth calibration better than 5 %.
NOTE The sputtered mass can also be determined by weighing samples before and after sputtering. However, this
requires the use of scales of extremely high accuracy, and the uncertainty in such measurements is generally greater than those
obtained by crater depth measurements.
6.3.4 Emission intensity measurements of calibration samples
The procedure for measuring the calibration samples is as follows:
a) prepare the surfaces of the calibration samples according to the instrument manufacturer’s instructions.
b) adjust the instrument to the current and voltage settings selected in 6.2, a preburn time of 100 s to 200 s and a
signal integration time of 5 s to 30 s.
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c) measure the emission intensities of the analytes zinc, aluminium, nickel, iron, silicon, copper and lead for each
calibration sample. Additional analytes, which are present in the calibration samples, may be measured
simultaneously. The units in which the intensities are given is of no importance, commonly used units are
counts per second (cps) or volts (V). Measure each sample at least two times and calculate the average
values.
6.3.5 Calculation of calibration constants
Calculation of calibration constants constitutes plotting data from the calibration measurements in appropriate
graphs and fitting to a curve by so-called regression calculation. Follow one of the procedures given in Annex A
(normative) appropriate for the instrument and software system available.
7 Verification of the analytical accuracy
Select from the set of calibration samples a few samples which contain the relevant analytes in concentrations as
close as possible to those found in the coating types to be determined. Prepare the sample surfaces in the same
way as for calibration measurements. Adjust the operating conditions for each sample to the same values as those
used during calibration. Run each sample as an unknown for a time resulting in a sputtered depth of 20 µm to
40 µm. Calculate the composition and sputtered depth using the calibration constants of the method.
Verify that the measured fraction of each analyte is accurate to within the acceptable uncertainty relative to the
certified value. The acceptable uncertainty cannot be uniquely defined for all analytes, but for majors, a relative
accuracy better than 5 % is achievable in most cases. Verify also that the measured sputtered depth is accurate to
within 10 % of that calculated from the known sputtering rate of the sample.
If coated test samples with well determined composition and coating thickness are available, run these samples as
unknowns and verify that measured composition and thickness are accurate within the acceptable uncertainty.
If unacceptably large deviations between measured and certified values are found, the instrument shall be drift
corrected as described in 6.3. The verification tests shall then be repeated. If the deviations are still unacceptably
large, the calibration shall be checked and possibly repeated.
8 Expression of results
8.1 Method of calculation
All analytical information obtained is contained in the quantitative depth profile (Figure 1).
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Key
1 Analyte weight in percent
2 Depth in micrometers
Figure 1 — Quantitative depth profile of a Galvanneal (ZnFe) coating on steel
In order to determine the total coating weights per element, the area under each curve is integrated for the total
depth of the coating. For the major elements, the following recommendation for determination of the integration
depth is given:
a) determine coating thickness as the depth where the concentration of the major element is reduced to 50 % of
the average value in the coating;
b) determine the width of the interface region (= the practical depth resolution) as the difference between the two
points in depth where the concentrations of the major element are 84 % and 15 % respectively of the average
value in the coating;
c) determine the integration depth as the sum of the coating thickness and the interface width.
The average concentrations of each element are determined as the fractions of the sum of the coating weights of
all elements present in the coating.
8.2 Precision
A planned trial of this method was carried out by eight laboratories, using six industrially produced coated steels as
test materials. Each laboratory made three determinations on one side of each material, calculating the integrated
coating weight of each element. The elements determined in the c
...
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