EN ISO 2177:1994
(Main)Metallic coatings - Measurement of coating thickness - Coulometric method by anodic dissolution (ISO 2177:1985)
Metallic coatings - Measurement of coating thickness - Coulometric method by anodic dissolution (ISO 2177:1985)
Metallische Überzüge - Schichtdickenmessung - Coulometrisches Verfahren durch anodisches Ablösen (ISO 2177:1985)
Diese Europäische Norm beschreibt ein coulometrisches Verfahren, bei dem durch anodisches Ablösen die Dicke metallischer Schichten gemessen wird. Typische Systeme von Schichten und Grundwerkstoffen, die nach diesem Verfahren gemessen werden können, sind in Tabelle 1 angegeben. Andere Kombinationen können mit gebräuchlichen Elektrolyten (siehe Anhang B) gemessen werden oder es können neue Elektrolyte dafür entwickelt werden. In beiden Fällen ist es jedoch notwendig, die Eignung des gesamten Systems zu überprüfen.
Revêtements métalliques - Mesurage de l'épaisseur - Méthode coulométrique par dissolution anodique (ISO 2177:1985)
Kovinske prevleke - Merjenje debeline prevleke - Kulometrična metoda z anodnim raztapljanjem (ISO 2177:1985)
General Information
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Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 2177:1999
01-oktober-1999
.RYLQVNHSUHYOHNH0HUMHQMHGHEHOLQHSUHYOHNH.XORPHWULþQDPHWRGD]DQRGQLP
UD]WDSOMDQMHP ,62
Metallic coatings - Measurement of coating thickness - Coulometric method by anodic
dissolution (ISO 2177:1985)
Metallische Überzüge - Schichtdickenmessung - Coulometrisches Verfahren durch
anodisches Ablösen (ISO 2177:1985)
Revetements métalliques - Mesurage de l'épaisseur - Méthode coulométrique par
dissolution anodique (ISO 2177:1985)
Ta slovenski standard je istoveten z: EN ISO 2177:1994
ICS:
17.040.20 Lastnosti površin Properties of surfaces
25.220.40 Kovinske prevleke Metallic coatings
SIST EN ISO 2177:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 2177:1999
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SIST EN ISO 2177:1999
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SIST EN ISO 2177:1999
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SIST EN ISO 2177:1999
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SIST EN ISO 2177:1999
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SIST EN ISO 2177:1999
Inte.rnational Standard
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION.MEIKJJYHAPO~HAR OPTAHM3AL&lFi fl0 CTAH~APTl43Al.WlM@ORGANISATION INTERNATIONALE DE NORMALISATION
Metallic coatings - Measurement of coating thickness -
Coulometric method by anodic dissolution
Revgtements m&alliques - Mesurage de l’epaisseur - Methode coulom&ique par dissolution anodique
Second edition - 19854545
Corrected and reprinted - 1986-03-01
w UDC 621.793 : 531.717 : 621.317.39 Ref. No. ISO 21774985 (E)
-
Descriptors : coatings, metal coatings, tests, determination, thickness, coulometric methods.
Price based on 9 pages
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SIST EN ISO 2177:1999
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of
national Standards bodies (ISO member bodies). The work of preparing International
Standards is normally carried out through ISO technical committees. Esch 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, govern-
mental and non-governmental, in liaison with ISO, also take patt in the work.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the ISO Council. They are approved in accordance with ISO procedures requiring at
least 75 % approval by the member bodies voting.
International Standard ISO 2177 was prepared by Technical Committee ISO/TC 107,
Metallic and o ther non-organic cos tings.
This second edition cancels and replaces the first edition (ISO 2177-19721, of which it
constitutes a technical revision.
Users should note that all International Standards undergo revision from time to time
and that any reference made herein to any other International Standard implies its
latest edition, unless otherwise stated.
0 International Organkation for Standardkation, 1985
Printed in Switzerland
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SIST EN ISO 2177:1999
ISO 2177-1985 (E)
INTERNATIONAL STANDARD
Measurement of coating thickness -
Metallic coatings -
Coulometric method by anodic dissolution +
of the coating thickness from the quantity of electricity (in
1 Scope and field of application
coulombs) used, which may in turn be calculated from
This International Standard specifies a coulometric method by
a) the time interval between the Start and the end of the
anodic dissolution for measuring the thickness of metallic
test, if it is conducted at constant current density;
coatings.
b) the integrated quantity of electricity used in dissolving
Typical combinations of coatings and Substrates that tan be the coatings.
tested by this method are given in table 1. Other combinations
may be tested with electrolytes in current use (sec annex BI, or
new electrolytes may be developed for them, but, in both 5 Instrumentation
cases, it is necessary to verify the suitability of the complete
System. 5.1 Suitable instruments may be constructed from readily
available components but proprietary instruments are usually
The method is also applicable to multi-layer Systems, for used (see annex A).
example Cu/Ni/Cr (sec also 8.6).
5.2 Proprietary direct reading instruments are available for
This method may be used to measure the thickness of coatings
use with electrolytes recommended by the manufacturer. Other
applied by various means, if due account is taken of special
instruments record the quantity of electricity, in coulombs,
features, such as the presence of an alloy layer. In some cases,
used in dissolving the coating from the measuring area (sec
the presence and thickness of diffusion layers tan also be
clause 31, usually in arbitrary units, from which the thickness is
measured. lt tan also be used to measure the thickness of
calculated using factors or tables.
coatings on cylindrical specimens and wires (sec 8.8).
With direct reading instruments, the calculation of thickness
from current density is made electronically.
2 Reference
5.3 The Performance of the instrument shall be checked
using specimens of known coating thickness. If the instrument
ISO 2064, Metallic and other non-organic coatings - D.efini-
readings agree to -+5 % of the known thicknesses of the
tions and conventions concerning the measurement of
specimens, the instrument may be used without further adjust-
thickness.
ment. Otherwise, the Cause of the discrepancy shall be re-
moved. Proprietary instruments shall always, however, be
calibrated in accordance with the manufacturer’s instructions.
3 Def initions
Suitable specimens of known coating thickness shall consist of
For the purpose of this International Standard, the definitions
the same type of coating and Substrate as the specimen to be
of ISO 2064, and the following, apply.
measured, and they shall have an accuracy of 5 % or better. If
measuring alloy coatings, the use of correct specimens is of
measuring area : The area of the significant surface over
particular importante.
which a Single measurement is made.
The measuring area for this method is the area enclosed by the
6 Electrolyte
sealing ring of the cell.
The electrolyte shall have a known, adequate shelf-life and shall
be such that:
4 Principle
a) there is no reaction with the coating metal in the
absence of an impressed flow of current;
Anodic dissolution of a weil-defined area of the coating using a
suitable electrolyte. Detection of the virtually complete dissolu- b) the coating dissolves anodically at an efficiency as close
tion of the coating by a rapid Change in cell voltage. Calculation to 100 % as possible;
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SIST EN ISO 2177:1999
ISO 21774985 (El
Table 1 - Typical combinations of coatings and Substrates which tan be tested by the coulometric method
Substrate (basis material)
Copper Nickel-cobalt-
Coating
Non-
iron alloys Silver
Aluminium * and topper Nickel Steel Zinc
metals
alloys (such as Kovar)
- -
Cadmium X X X x - X
- -
Chromium X X x - X
X
Only on brass and
x
- -
Copper X X X
X
topper-beryllium
Lead X X X X .X x - X
- -
X x -
Nickel a X X X
-
Nickel, autocatalytic ** X X X X x - X
- -
X x -
Silver X X X
- -
Tin X X X x - X
-
Tin-lead alloys *** X X X X x - X
- -
X X x - X
Zinc X
* The detection of the Change in the cell voltage may be difficult with some aluminium alloys.
** The coulometric method tan only be used if the phosphorus or boron contents of these coatings are within certain limits.
*** The method is sensitive to alloy composition.
c) a detectable sharp Change in electrode potential occurs be eliminated, or reduced, by increasing the rate of dissolution,
as the coating is penetrated and an increasing area of i.e. by increasing the current density used in the test.
Substrate is exposed ;
7.2 Current Variation
d) the test area exposed in the test cell is completely
wetted.
For instruments using the constant current and time measuring
The electrolyte shall be Chosen in relation to the coating and technique, current Variation will Cause errors. For instruments
using a current-time integrator, too laige a Change in current
Substrate materials, the current density and electrolyte circula-
tion within the test cell. Typical electrolytes that have been may Change the anode current efficiency or interfere with the
end-point causing an error.
found satisfactory for use with ,one type of test apparatus for
testing various electrodeposited coatings on specific Substrates
are described in annex B.
7.3 Area Variation
For proprietary instruments, the electrolytes shall normally be
\ The accuracy of the thickness measurement will be no better
Chosen on the recommendations of the manufacturer.
than the accuracy to which the measuring area is known. Area
variations due to gasket wear, gasket pressure, etc., may lead
to measurement errors. Much greater accuracy tan be obtained
if the electrolytic cells are so designed that sealing rings con-
7 Factors affecting the measuring accuracy
sistently give weil-defined measuring areas? In some cases it
may be advantageous to measure the area after it has been
The following factors may affect the accuracy of coating
deplated and compensate accordingly.
thickness measurements.
7.1 Coating thickness 7.4 Agitation (if required)
Generally, the accuracy is lower than Optimum for coating
Inadequate agitation tan Cause a false end-point.
thicknesses greater than 50 Fm and less than 0,2 Pm, unless
special equipment is used.
7.5 Alloy layer between coating and Substrate
With coatings thicker than 50 Pm, there may be an appreciable
The measurement of coating thickness by the coulometric
amount of bevelling or undercutting as the anodic dissolution
method assumes implicitly that a sharply defined interface
proceeds. The amount of bevelling is largely dependent on the
method employed for stirring the electrolyte. Undercutting may exists between the coating and the Substrate. If an alloy layer
1) Error due to variations of the measuring area may, in some instances, be minimized by modifying the instrument calibration using coating
thickness calibration Standards. Such Standards should create similar test conditions to those during actual tests, particularly if testing curved
surfaces.
2
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SIST EN ISO 2177:1999
ISO 21774985 (El
8 Procedure
exists between the coating and the Substrate as, for example,
in the case of coatings applied by hot dipping l), the coulo-
metric end-point may occur at some Point within the alloy
8.1 General
layer, thus giving a high value for the thickness of the unalloyed
coatings. .
If commercial equipment is used, follow the manufacturer’s in-
structions with respect to the operating procedure for measure-
7.6 Purity of coatings
ment, the electrolytes and, if necessary, calibration (see 5.3).
Appropriate attention shall be given to the factors listed in
Materials that co-deposit with a coating metal (including alloy-
clause 7.
ing metals) may Change the effective electrochemical equiv-
alent of the coating metal, the anode current efficiency, and the
8.2 Pre-set voltage
coating density.
If using instruments that require a pre-set voltage, it should be
7.7 Condition of test surface
noted that the actual value is dependent ,on the parttcular
metallic coating, current density, electrolyte concentration and
Oil, grease, paint, corrosion products, polishing ingredients,
temperature, and circuit resistance, for example lead-out con-
conversion coatings, passivity of nicke1 coatings, etc., may in-
nections. For these reasons, it is considered advisable to first
tet-fere with the test.
perform an evaluation test.
7.8 Density of coating material
8.3 Preparation of test surface
Because the coulometric method measures intrinsically mass
If necessary, clean the test surface (see 7.7) with a suitable
per unit area, variations in density from the normal density of
organic solvent. lt may also be necessary to activate the test
the coating metal will Cause corresponding variations in linear
surface by mechanical or Chemical means, but care should then
thickness measurements. Normal variations of the composition
be taken to avoid removal of metal.
of an alloy result in small, but significant changes in alloy
density and its electrochemical equivalent.
8.4 Gell application
7.9 Cleanliness of the cell
Press the electrolytic cell, fitted with its flexible sealing ring, on
Deposition of metal may take place on the cathode in some
to the coating so that a known area is exposed to the test elec-
electrolytes. This deposit tan alter the cell voltages or block the
trolyte. If the cell body is metallic, for example stainless steel, it
cell aperture. lt is, therefore, essential to keep the cathode
normally forms the cell cathode, but, otherwise, insert a
clean.
suitable cathode (incorporated in some instruments as part of
the electrotyte agitation mechanism).
7.10 Cleanliness of electrical connections
8.5 Electrolysis
In the case of instruments other than the constant current type,
if the electrical connections are not clean, the current/potential
Introduce the appropriate electrolyte and make sure that no air
relationship will be disturbed and false end-points obtained.
bubbles occur on the measuring surface. If required, put the
agitation mechanism into the cell. Make the electrical connec-
7.11 Calibration Standards (if used)
tions, and operate the agitator as appropriate. Continue elec-
trolysis until dissolution of the coating is complete, as indicated
Measurements made using calibration Standards are subject to
by a sharp Change in the anode potential or cell voltage, or by
the additional error of the Standards. If the thickness of alloy
the Operation of the automatic Cut-out.
coatings is being determined, it is usually necessary to use
coating Standards and to test them using the same procedure.
8.6 Undercoats
7.12 Non-uniform dissolution
When one or more undercoats are to be measured, after
measuring the top coating ensure that the top coat has first
If the rate of dissolution is not uniform over the measuring area,
been completely removed from the whole of the measuring
a premature end-point may be obtained, and yield low results.
area. Remove the electrolyte from the cell with a suitable suc-
Hence, one should examine the surface after the test to verify
tion device, and thoroughly rinse out the cell with distilled or
that most of the coating has dissolved. On some Substrates,
demineralized water.
however, a visible, but insignificant, portion of the coating may
remain. -
DO not disturb the cell at any ti me during these operations.
Abandon the test if occurred.
the slightest displacement has
The presence of other material in the coating, the roughness of
the coating surface and interface and the presence of porosity
Reset the instrument controls introduce
for the next coating,
in the coating tan Cause fluctuation of the cell voltage. Such
the appropriate electrolyte and continue the test as before.
fluctuations tan prematurely affect the end-point.
1) See the footnote to clause A.1.
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SIST EN ISO 2177:1999
ISO 21774985 (El
The thickness may also be expressed as:
8.7 Examination after test
After completion of the test(s), remove the electrolyte from the
cell, rinse out with water, lift off the cell and examine the where X is a constant for a given metal coating, electrolyte and
specimen to ensure that the removal of the coating is complete cell. The value of X tan either be calculated theoretically from
over the area enclosed by the seal (sec 7.12). the area of the test specimen exposed by the sealing ring, the
efficiency of anodic dissolution (usually 100 %) and the elec-
trochemical equivalent and density of the coating metal, or tan
8.8 Coatings on cylindrical specimens
be determined experimentally by measuring a coating of known
thickness.
If the surface area is too small to use the normal cell with a flexi-
ble gasket, replace it by an electrolyte Container and an ap-
With most commercial instruments, the thickness is either read
propriate holding device, using an agitator if necessary. This
directly from the instrument or the instrument reading is con-
device shall be adjustable and shall be pre-set to allow a known
verted to thickness by applying a factor appropriate to the
length of specimen to be immersed. For direct reading in-
measuring area exposed by the cell and the coating metal.
struments, especially those with alternative cell sizes, calculate
the length of specimen to be immersed so that the same known
surface area is presented to the cathode as for a test cell.
10 Measurement uncertainty
In the majority of applications, the same electrolyte tan be used
but, in Order to obtain the Optimum instrument sensitivity and
The test equipment and the procedure shall be such that the
accuracy, the operating conditions may have to be modified,
coating thickness tan be measured to within 10 % of its true
for example the tut-off voltage and deplating current.
. thickness.
NOTE - An exact deplating area is necessary for accuracy and the
main Source of error is due to the meniscus and current field at the
11 Test report
electrolyte surface.
The test report shall include the following information:
9 Expression of results
a) a reference to this International Standard;
is given by the
The coating thickness, d, in micrometres,
an identification of the test specimen ;
b)
equation
QE
c) the area, in Square centimetres, over
d = look-
measurements were made
At?
the location of the reference area;
d)
k is the current efficiency of the dissolution process (equal
e) the IocatioM on the item at the tests
to 100 in the case of 100 % eff iciency) ;
were carried out;
E is the electrochemical eq uivalent, in grams per coulomb,
1 conditions of the test;
of the coating metal for the
the identity of the electrolyte used;
fl
Square centimetres, from which the
A is the area, in
g) the measured thickness in micrometres at each area at
‘coating is dissolved , i.e. the measuring area ;
which the tests were carried out; the number of
e is the density, i
...
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