SIST EN ISO 10308:2006

SLOVENSKI STANDARD
01-marec-2006
1DGRPHãþD
SIST EN ISO 10308:1999
Kovinske prevleke – Pregled preskusov za ugotavljanje poroznosti (ISO
10308:2006)
Metallic coatings - Review of porosity tests (ISO 10308:2006)
Metallische Überzüge - Übersicht der Porenprüfverfahren (ISO 10308:2006)
Revetements métalliques - Passage en revue des essais de porosité (ISO 10308:2006)
Ta slovenski standard je istoveten z: EN ISO 10308:2006
ICS:
25.220.40 Kovinske prevleke Metallic coatings
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 10308
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2006
ICS 25.220.40 Supersedes EN ISO 10308:1997
English Version
Metallic coatings - Review of porosity tests (ISO 10308:2006)
Revêtements métalliques - Passage en revue des essais Metallische Überzüge - Übersicht der Porenprüfverfahren
de porosité (ISO 10308:2006) (ISO 10308:2006)
This European Standard was approved by CEN on 28 December 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
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versions.
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Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
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© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 10308:2006: E
worldwide for CEN national Members.

Foreword
This document (EN ISO 10308:2006) has been prepared by Technical Committee ISO/TC 107
"Metallic and other inorganic coatings" in collaboration with Technical Committee CEN/TC 262
"Metallic and other inorganic coatings", the secretariat of which is held by BSI.

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 July 2006, and conflicting national standards
shall be withdrawn at the latest by July 2006.

This document supersedes EN ISO 10308:1997.

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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice
The text of ISO 10308:2006 has been approved by CEN as EN ISO 10308:2006 without any
modifications.
INTERNATIONAL ISO
STANDARD 10308
Second edition
2006-01-15
Metallic coatings — Review of porosity
tests
Revêtements métalliques — Passage en revue des essais de porosité

Reference number
ISO 10308:2006(E)
©
ISO 2006
ISO 10308:2006(E)
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ii © ISO 2006 – All rights reserved

ISO 10308:2006(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle. 2
5 Common features of porosity tests . 2
6 Test specimens . 2
7 Specific porosity tests. 2
7.1 Alizarin test. 2
7.2 Anthraquinone test. 3
7.3 Cadmium sulfide test. 3
7.4 Copper sulfate (Preece) test . 3
7.5 Copper sulfate (Dupernell) test . 3
7.6 Corrodkote test (CORR) . 4
7.7 Electrographic tests . 4
7.8 Ferrocyanide test. 5
7.9 Ferron test . 5
7.10 Ferroxyl test . 6
7.11 Flowers-of-sulfur porosity test. 6
7.12 Hot-water test . 6
7.13 Hydrogen sulfide or sulfur dioxide/hydrogen sulfide test. 6
7.14 Haematoxylin test . 7
7.15 Magneson test. 7
7.16 Nitric acid vapour test . 7
7.17 Oxine test. 8
7.18 Permanganate test. 8
7.19 Polysulfide test . 8
7.20 Porotest test . 8
7.21 Salt spray tests [neutral (NSS), acetic (AASS) and cuproacetic (CASS)]. 9
7.22 Sulfur dioxide test. 9
7.23 Sulfurous acid/sulfur dioxide vapour test. 9
7.24 Thiocyanate test. 9
7.25 Thioacetamlde test (TAA) . 10
7.26 Watch-case acetic acid test . 10
7.27 Watch-case sodium bisulfite test. 10
Annex A (normative) Tables of porosity tests. 11
Annex B (informative) Typical report and evaluation of porosity tests. 14
Annex C (informative) Schematic representation of types of pore. 16
Annex D (informative) Classification of discontinuities in metallic and other inorganic coatings . 17
Annex E (informative) Classification of methods of testing coating porosity. 18
Annex F (informative) Alphabetical list of tests by substrate and coating . 19
Bibliography . 30

ISO 10308:2006(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 10308 was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings,
Subcommittee SC 7, Corrosion tests.
This second edition cancels and replaces the first edition (ISO 10308:1995), which has been technically
revised.
iv © ISO 2006 – All rights reserved

INTERNATIONAL STANDARD ISO 10308:2006(E)

Metallic coatings — Review of porosity tests
WARNING —  This international Standard calls for the use of substances and/or procedures that can
be injurious to health if adequate precautions are not taken. It refers only to technical suitability and in
no way absolves either the designer, the producer, the supplier or the user from statutory and all
other legal obligations relating to health and safety at any stage of manufacture or use.
1 Scope
This International Standard reviews published methods for revealing pores (see ISO 2080) and discontinuities
in coatings of aluminium, anodized aluminium, brass, cadmium, chromium, cobalt, copper, gold, indium, lead,
nickel, nickel-boron, nickel-cobalt, nickel-iron, nickel-phosphorus, palladium, platinum, vitreous or porcelain
enamel, rhodium, silver, tin, tin-lead, tin-nickel, tin-zinc, zinc and chromate or phosphate conversion coatings
(including associated organic films) on aluminium, beryllium-copper, brass, copper, iron, NiFeCo alloys,
magnesium, nickel, nickel-boron, nickel-phosphorus, phosphor-bronze, silver, steel, tin-nickel and zinc alloy
basis metal.
The tests summarized in this International Standard are designed to react with the substrate when exposed,
by a discontinuity, in such a way as to form an observable reaction product.
NOTE 1 Pores are usually perpendicular to the coating surface but may be inclined to the coating surface. They are
frequently cylindrical in shape but may also assume a twisted shape (see Annex C).
NOTE 2 Porosity may vary in size from the submicroscopic, invisible using a light microscope, to the microscopic,
visible from × 10 to × 1 000, to the macroscopic, visible to the naked eye.
NOTE 3 Porosity may be visibly indicated by discolouration of the coated surface.
NOTE 4 Porosity in a coating is not always detrimental. In microdiscontinuous chromium, for example, porosity or
microcracking is beneficial and tests are conducted to indicate the pores.
NOTE 5 Results obtained from porosity tests, expressed in terms such as pores per square centimeter, are relative
values associated with the specific test method used and the magnification used during examination. Annex B gives
typical report criteria.
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 2080:1981, Electroplating and related processes — Vocabulary
ISO 10289:1999, Methods for corrosion testing of metallic and other inorganic coatings on metallic
substrates — Rating of test specimens and manufactured articles subjected to corrosion tests
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 2080 and the following apply.
ISO 10308:2006(E)
3.1
discontinuities
cracks, micro-holes, pits, scratches or any other opening in the coating surface that exposes a different
underlying metal
NOTE For further information on discontinuities, see Annex D and reference [1] in the Bibliography.
4 Principle
The results of porosity tests are the end products of a chemical reaction with a metallic substrate. Some occur
in situ, others on paper or in a gel coating. Observations are made that are consistent with the test method
and the items being tested, as specified by the purchaser. These may be visual inspections (naked eye) or at
× 10 magnification (microscope). Other methods may involve enlarged photographs or photo-micrographs.
See references [1,2, 3, 5 and 6] in the Bibliography (see also Annex A for a tabular summary of the porosity
tests and Annex D for a classification of discontinuities).
5 Common features of porosity tests
Porosity tests differ from corrosion tests and, particularly, ageing tests regarding test duration. Porosity tests
are primarily short-time tests. A good porosity test process shall clean, depolarize and activate the substrate
metal exposed by the pore and attack it to such a degree as to cause the reaction product to fill the pore to the
surface of the coating. The corrosive shall not react with the coating. It is essential that the time of reaction be
limited, particularly with thin coatings, since the corrosive will attack the substrate in all directions and, in so
doing, will undermine the coatings resulting in misleading observations. When the corrosion product is soluble
in the reagent, the precipitating indicator is used to form the reaction product. (See Annex E for a classification
of methods of porosity testing).
6 Test specimens
Porosity tests are generally destructive in nature and are designed to assess the quality of the coating process
of the substrate. Therefore, as a rule, separate test specimens are not used.
7 Specific porosity tests
7.1 Alizarin test
7.1.1 Scope
For coatings of chromium (including Cr/Ni/Cu and Cr/Ni/Ni), cobalt, copper, nickel, nickel-boron, nickel-cobalt,
nickel-iron and nickel-phosphorus on aluminium substrate.
7.1.2 Summary of method
The test specimens are treated with sodium hydroxide, sodium alizarin sulfonate and glacial acetic acid under
defined conditions. Formation of red markings or spots indicates porosity. Details of the test procedure can be
found in references [9, 21 and 25] in the Bibliography.
2 © ISO 2006 – All rights reserved

ISO 10308:2006(E)
7.2 Anthraquinone test
7.2.1 Scope
For coatings of chromium (including Cr/Ni/Ni), cobalt, nickel, nickel-boron, nickel-cobalt, nickel-iron and nickel-
phosphorus on aluminium, magnesium or zinc alloy substrates.
7.2.2 Summary of method
The test specimens are treated with sodium hydroxide and potassium 1-aminoanthraquinone-2-carboxylic
acid under defined conditions. The formation of red markings or spots indicates porosity. Details of the test
procedure can be found in reference [13] in the Bibliography.
7.3 Cadmium sulfide test
7.3.1 Scope
For metallic coatings of chromium (including Cr/Ni/Ni), gold, palladium, platinum and rhodium on beryllium-
copper, brass, copper, phosphor-bronze and silver substrates.
7.3.2 Summary of method
Filter paper is soaked in cadmium chloride and then treated with sodium sulfide to precipitate cadmium sulfide.
The sample is sandwiched between the cadmium sulfide paper (which acts as the anode) and the moistened
blotting paper fastened to a high-purity clean aluminium or stainless steel platen (which acts as the cathode).
D.C. current is applied for a specific time. Brown stains on the paper indicate pores. Details of the test
procedure can be found in ISO 4524-3.
7.4 Copper sulfate (Preece) test
7.4.1 Scope
Variation A. For coatings of cadmium and zinc on iron, steel or iron-based alloy substrates.
Variation B. For thin (< 5 µm) anodic oxide coatings on aluminium and aluminium alloy substrates.
7.4.2 Summary of method
The test specimen is immersed in a solution of copper sulfate; different solution compositions are used for
aluminium alloy and iron alloy substrates. Reddish markings or spots, of copper, indicate pores on ferrous
substrates; black markings or spots indicate pores on aluminium alloy substrates. Details of the test
procedures can be found in ISO 2085. See also reference [26] in the Bibliography.
7.5 Copper sulfate (Dupernell) test
7.5.1 Scope
For coatings of chromium and micro-cracked or microporous chromium on nickel/copper or nickel/nickel on
iron, steel, zinc alloys, copper and copper alloys, aluminium and aluminium alloy, plastic substrates.
7.5.2 Summary of method
The test specimen is used as the cathode in an acid copper plating bath. Copper is deposited only where the
basis metal or the substrate is exposed, the chromium remaining passive. After the test, examine the surface
for cracks using an optical microscope. Details of the test procedure can be found in ISO 1456, ISO 4525 and
ISO 6158. See also references [27 and 28] in the Bibliography.
ISO 10308:2006(E)
7.6 Corrodkote test (CORR)
7.6.1 Scope
For coatings of chromium and micro-cracked or microporous chromium on nickel/copper or nickel/nickel on
aluminium alloy, plastic, steel and iron alloy or zinc alloy substrates.
7.6.2 Summary of method
The test specimen is coated with a slurry of corrosive salts and dried. The coated specimens are exposed to
high relative humidity for a specified period of time, then cleaned and treated for redeveloping the points of
failure, e.g. in a salt spray cabinet. Porosity is indicated by black markings or red rust on the iron-based
substrates or by white markings on the aluminium and zinc substrates (see ISO 10289). Details of the test
procedure can be found in ISO 4541. See also reference [ 38] in the Bibliography.
7.7 Electrographic tests
7.7.1 Scope
Variation A. Acrylamide electrography (See warning in 7.7.2.)
For gold coatings on nickel and silver, or nickel coatings on copper substrates.
Variation B. Gel bulk electrography.
For gold, cobalt, nickel and palladium coatings on copper; gold, copper, cobalt and paIIadium coatings on
nickel; gold on silver substrates.
Variation C. Paper electrography.
For the following combinations of indicator-coatings/substrate that have flat or nearly flat surfaces.
Indicator Coating/substrate
1. Cadmium sulfide Chromium, gold, palladium, platinum and rhodium on beryllium-copper, brass,
copper, phosphor-bronze and silver substrates
2. Dimethylglyoxime Gold, palladium, platinum, rhodium and silver on brass, beryllium-copper, copper,
phosphor-bronze, nickel, nickel-boron and nickel-phosphorus substrates
3. Dithioxamide Chromium, gold, palladium, platinum and rhodium on beryllium-copper, brass,
copper and phosphor-bronze substrates
4. Nioxime Gold, palladium, platinum and rhodium on nickel, nickel-boron, nickel-iron, nickel-
phosphorus and tin-nickel substrates
5. Potassium ferrocyanide Chromium, gold, palladium platinum and rhodium on brass, beryllium-copper,
copper and phosphor-bronze substrates
6. Potassium ferricyanide Cadmium, nickel, tin and zinc on brass, silver and steel substrates
7. Magneson Chromium, cobalt, copper, nickel, nickel-boron, nickel-cobalt, nickel-iron and
nickel-phosphorus on magnesium substrates
4 © ISO 2006 – All rights reserved

ISO 10308:2006(E)
7.7.2 Summary of methods
Variation A. Acrylamide electrography.
Acrylamide solution containing a hardener and an indicator is poured onto the sample shortly before
gelatinizing. The sample is made the anode in a cell with a chloride solution and electrolized. Pores are
revealed as coloured marks or spots. Details of the test procedure can be found in reference [7] in the
Bibliography.
WARNING —  Acrylamide has been identified as a neurotoxin and carcinogen; use with extreme
caution.
Variation B. Gel bulk electrography.
A mixture of clear gelatin, conducting salts and an indicator are poured into an electrolytic cell with a gold or
platinum cathode and with the specimen as the anode. The composite gel solution is allowed to solidify,
following which the cell is electrolized. Pores are revealed as coloured spots or blooms. Details of the test
procedure can be found in ISO 15720. See also reference [39] in the Bibliography.
Variation C. Paper electrography.
Test specimens are sandwiched as an anode between electrolyte-soaked paper and indicator paper and
clamped with two cathode covers (of non-reactive materials such as gold or stainless steel). A specified

2 2
current (usually 0,15 mA/cm to 1,55 mA/cm ) for a specified time (usually 10 s to 30 s) is applied. After
exposure, the test paper is wetted with indicator and allowed to dry. Pores are revealed as coloured spots.
A variety of commercially prepared test papers is available. Details of the test procedures can be found in
ISO 4524-3. See also references [15, 18, 24 and 29] in the Bibliography.
7.8 Ferrocyanide test
7.8.1 Scope
For coatings of chromium, cobalt, gold, nickel, nickel-boron, nickel-iron, nickel-phosphorus, palladium,
platinum and rhodium on copper substrate.
7.8.2 Summary of method
The test specimens are treated with glacial acetic acid and potassium ferrocyanide under defined conditions.
Formation of brown markings or spots indicates porosity. Details of the test procedure can be found in
references [12 and 37] in the Bibliography.
7.9 Ferron test
7.9.1 Scope
For coatings of aluminium, brass, cadmium, chromium, cobalt, indium, lead, nickel, nickel-boron, nickel-
phosphorus, organic films, silver, tin, tin-lead, tin-nickel, tin-zinc and zinc, on iron and steel substrates.
7.9.2 Summary of method
The test specimens are treated with acid and a 0,1 % solution of ferron (8-hydroxyquinoline 7-iodo-5-sulfonic
acid), under defined conditions. Formation of red markings or spots indicates porosity. Details of the test
procedure can be found in reference [4] in the Bibliography.
ISO 10308:2006(E)
7.10 Ferroxyl test
7.10.1 Scope
For metallic coatings, such as brass, chromium, cobalt, copper, gold, indium, lead, nickel, nickel-boron, nickel-
phosphorus, organic films, silver, tin, tin-lead and tin-nickel, that are resistant, for the duration of the test
period, to ferricyanide and chloride and are also cathodic to their iron or steel alloy substrates.
7.10.2 Summary of method
Electrolyte-wetted, gel-chloride-treated paper strips are placed firmly in contact with test specimen surfaces
for a specified time. After the allotted time, the paper strips are wetted adequately with ferricyanide indicator
solution. Blue markings or spots indicate pores. Details of the test procedure can be found in ISO 4526 and
ISO 10309. See also references [20 and 30] in the Bibliography.
7.11 Flowers-of-sulfur porosity test
7.11.1 Scope
For coatings of gold, nickel, tin, tin-lead, palladium and their alloys on copper, copper alloy or silver substrates.
It may be used with other coatings that do not significantly tarnish in a reduced-sulfur atmosphere.
7.11.2 Summary of method
Test specimens are suspended on non-reactive supports in a non-reactive container with controlled humidity
and elevated temperature (50 °C) for a specified time in a closed system over the flowers of sulfur. Brown or
black tarnish marks or spots indicate porosity. Details of the test procedure can be found in ISO 12687. See
also reference [31] in the Bibliography.
7.12 Hot-water test
7.12.1 Scope
For metallic coatings cathodic to a ferrous substrate: for example, brass, copper, gold, indium, nickel, nickel-
boron, nickel-phosphorus, tin, tin-lead and tin-nickel on iron, NiFeCo alloys or steel substrates; organic films
on steel substrate.
7.12.2 Summary of method
The test specimens are placed in a glass vessel filled with distilled or deionized and aerated water (pH 6,0 to
7,5, conductivity not higher than 0,5 mS/m). Water is heated to 85 °C and the temperature shall be maintained
throughout 60 min (test period). After exposure and drying, black markings or spots and red rust indicate
porosity. Details of the test procedure can be found in ISO 4526. See also references [25 and 30] in the
Bibliography.
7.13 Hydrogen sulfide or sulfur dioxide/hydrogen sulfide test
7.13.1 Scope
Variation A. For coatings of less than 5 µm of gold, palladium or rhodium on beryllium-copper, brass, copper,
phosphor-bronze and silver substrates.
Variation B. For coatings of more than 5 µm of gold, palladium, rhodium, tin, tin-lead, or tin-nickel on
beryllium-copper, brass, copper, nickel, nickel-boron, nickel-phosphorus, phosphor-bronze or silver substrates.
6 © ISO 2006 – All rights reserved

ISO 10308:2006(E)
7.13.2 Summary of method
Variation A. Test specimens are suspended on non-reactive supports in a non-reactive container with a
freshly generated hydrogen sulfide atmosphere for a specified time, usually 24 h. Discolouration on the
surface indicates porosity. Details of the test procedure can be found in reference [41] in the Bibliography. See
also reference [53] in the Bibliography.
Variation B. Test specimens are suspended on non-reactive supports in a non-reactive container with a
freshly generated sulfur dioxide atmosphere for a specified time, usually 24 h, followed by freshly generated
hydrogen sulfide atmosphere for a specified time, usually 24 h. Discolouration on the surface indicates
porosity. Details of the test procedure can be found in reference [17] in the Bibliography.
7.14 Haematoxylin test
7.14.1 Scope
For coatings of brass on aluminium; or silver on brass and copper substrates.
7.14.2 Summary of method
Paper strips treated with haematoxylin are immersed in water and are placed firmly in contact with test
specimen surfaces for a specified time. After the allotted time, the paper strips are examined for blue markings
or spots which indicate pores. Details of this test can be found in references [8 and 11] in the Bibliography.
7.15 Magneson test
7.15.1 Scope
For coatings of chromium, cobalt, copper, nickel, nickel-boron, nickel-cobalt, nickel-iron and nickel-
phosphorus on magnesium substrate.
7.15.2 Summary of method
The test specimens are treated with sodium hydroxide. Dry magneson test paper, prepared by dipping filter
paper in a 0,01 % alcohol solution of ρ-nitrobenzene-azo-resorcinol is applied to the treated surface.
Formation of blue markings or spots on a red background indicates porosity. Details of the test procedure can
be found in reference [15] in the Bibliography.
7.16 Nitric acid vapour test
7.16.1 Scope
For gold coatings on substrates of copper, nickel and their alloys.
7.16.2 Summary of method
A stabilized acid atmosphere is established by placing concentrated nitric acid in a non-reactive container,
which is covered and left to stand for 0,5 h at a specified ambience.
Test specimens are suspended in this closed-system atmosphere and exposed for 60 min ± 5 min. After
exposure, the specimens are heated to dry the reaction products. Each reaction-product marking or spot,
usually protruding, indicates a pore in the coating. Details of the test procedure can be found in ISO 14647.
See also reference [32] in the Bibliography.
ISO 10308:2006(E)
7.17 Oxine test
7.17.1 Scope
For coatings of chromium, cobalt, copper, nickel, nickel-boron, nickel-cobalt, nickel-iron and nickel-
phosphorus on aluminium, magnesium and zinc substrates.
7.17.2 Summary of method
The test specimens are treated with sodium hydroxide. Dry oxine test paper, prepared by dipping filter paper
in a 5 % alcohol solution of 8-hydroxyquinoline, is applied to the treated surface. Formation of coloured
markings or spots indicates porosity. Details of the test procedure can be found in references [10 and 14] in
the Bibliography.
7.18 Permanganate test
7.18.1 Scope
For coatings of aluminium, cadmium and zinc on iron, steel or iron-based alloy substrates.
7.18.2 Summary of method
The test specimen is immersed in a dilute solution of potassium permanganate. Black markings or spots, of
manganese dioxide, indicate pores. Details of this test can be found in reference [8] in the Bibliography.
7.19 Polysulfide test
7.19.1 Scope
For metallic coatings of tin, tin-nickel and tin-zinc on beryllium-copper, brass, copper and phosphor-bronze
substrates.
7.19.2 Summary of method
Coated parts are solvent-cleaned and then immersed in a solution of sodium polysulfide. Formation of black
markings or spots indicates pores. Details of the test procedure can be found in reference [32] in the
Bibliography.
7.20 Porotest test
7.20.1 Scope
For metallic coatings, such as brass, chromium, copper, gold, nickel, nickel-boron, nickel-phosphorus, tin, tin-
nickel and their alloys, which are cathodic to their iron, steel or iron-based alloy substrates.
7.20.2 Summary of method
Paper strips, treated with α-nitroso-β-naphthol, are immersed in water — or, to speed up the reaction, 5 %
sodium chloride — are placed firmly in contact with test specimen surfaces for a specified time. After the
allotted time, the paper strips are examined for green markings or spots which indicate pores. Details of this
test can be found in reference [8] in the Bibliography.
8 © ISO 2006 – All rights reserved

ISO 10308:2006(E)
7.21 Salt spray tests [neutral (NSS), acetic (AASS) and cuproacetic (CASS)]
7.21.1 Scope
For metallic coatings, such as brass, chromium, cobalt, copper, gold, lead, nickel, nickel-boron,
nickel-phosphorus, tin, tin-lead and tin-nickel, that are resistant, for the duration of the test period, to chloride
and which are also cathodic to their iron, steel, or iron-based alloy substrates. The test is also suitable for
coatings of chromium on nickel/copper and chromium on nickel/nickel on aluminium, magnesium, zinc and
plastic substrates.
7.21.2 Summary of method
Specimens are placed in a cabinet and subjected to a fog spray of 5 % sodium chloride solutions. Porosity is
indicated by black markings or spots and red rust on substrates of iron, steel or iron-based alloys, or white
markings, spots or blisters in the coating on substrates of aluminium, magnesium or zinc alloy (see
ISO 10289). Details of the test procedure can be found in ISO 9227. See also references [22, 23, 34 and 35]
in the Bibliography.
7.22 Sulfur dioxide test
7.22.1 Scope
Variation A. For coatings of gold on copper, copper alloy and nickel substrates.
Variation B. For coatings of gold on silver substrates.
Variation C. For coatings of tin, tin-lead and tin-nickel on copper, copper alloy and steel substrates.
7.22.2 Summary of method
Test specimens are suspended on non-reactive supports in a non-reactive container with a freshly generated
sulfur dioxide atmosphere for a specified time, usually 24 h. The concentrations of sulfur dioxide, generated as
the corrosive atmosphere, are selected for the specific variation A, B or C (coating and substrate combination).
Colour on the surface indicates porosity. Details of the test procedure can be found in ISO 6988. See also
references [19, 22, 36, 37 and 53] in the Bibliography.
7.23 Sulfurous acid/sulfur dioxide vapour test
7.23.1 Scope
For coatings of gold and palladium on substrates of copper, nickel and their alloys.
7.23.2 Summary of method
Test specimens are suspended on non-reactive supports in a non-reactive container with a sulfurous
acid/sulfur dioxide atmosphere for a specified time, usually 24 h. Colour on the surface indicates porosity.
Details of the test procedure can be found in ISO 15721. See also reference [40] in the Bibliography.
7.24 Thiocyanate test
7.24.1 Scope
For metallic coatings, such as chromium, copper, nickel, nickel-boron, nickel-phosphorus, tin, tin-nickel and
their alloys, that are resistant to thiocyanate and chloride during the time period of the test, and which are also
cathodic to their iron or steel alloy substrates.
ISO 10308:2006(E)
7.24.2 Summary of method
Electrolyte-wetted, gel-chloride-treated paper strips are placed firmly in contact with test specimen surfaces
for a specified time. After the allotted time, the paper strips are wetted adequately with thiocyanate indicator
solution. Red markings or spots indicate pores. Details of this test procedure can be found in reference [8] in
the Bibliography.
7.25 Thioacetamlde test (TAA)
7.25.1 Scope
For gold, nickel, tin and tin-nickel coatings on copper, copper alloys and silver substrates. This test can also
be used for organic coatings on brass, copper or silver substrates.
7.25.2 Summary of method
Test specimens are suspended on non-reactive supports in a non-reactive container with a saturated solution
of sodium acetate for maintaining the relative humidity of 75 %, and crystals of thioacetamide (at least 50 mg
per square decimetre) at 25 °C for a specified time in the closed system. Coloured spots, pits, cracks, blisters,
etc. indicate porosity. Details of the test procedure can be found in ISO 4538. See also reference [16] in the
Bibliography.
7.26 Watch-case acetic acid test
7.26.1 Scope
For gold coatings on cuprous alloy with or without nickel, and die-cast zinc-based alloy substrates.
7.26.2 Summary of method
Test specimens are suspended on non-reactive supports in a non-reactive vessel and exposed to vapours of
acetic acid for 24 h at 23 °C ± 2 °C. Pores are revealed as green markings on cuprous alloy substrates or
white markings on die-cast zinc-based alloy substrates. Details of the test procedure can be found in
ISO 3160-2.
7.27 Watch-case sodium bisulfite test
7.27.1 Scope
For gold coatings on ferrous alloy substrates.
7.27.2 Summary of method
Test specimens are suspended on non-reactive supports in a non-reactive vessel and exposed to vapours of
sodium bisulfite for 24 h at 23 °C ± 2 °C. Every trace of corrosion on the significant surface indicates porosity.
Details of the test procedure can be found in ISO 3160-2.

10 © ISO 2006 – All rights reserved

ISO 10308:2006(E)
Annex A
(normative)
Tables of porosity tests
ISO 10308:2006(E)
Table A.1 — Substrate or underlayer: aluminium alloys, copper alloys, iron alloys
Substrate or underlayer
Copper alloys Iron alloys
Coating
Aluminium
Beryllium Phosphor- Cast iron and
alloys
Brass Copper NiFeCo
Copper bronze steel
Aluminium   9,18 9
Anodized aluminium 4B
Brass 14   9,10,12,20,21 9,10,12
Cadmium  7C6  4A,7C6,9,18 4A,9
Chromate conversion 21  11
Chromium 1,2,5,6,17 3,7C1,7C3, 3,7C1,7C3, 3,5,7C1,7C3, 3,7C1,7C3, 5,6,9,10,12,20, 5,6,9,10,
7C5 7C5 7C5,8 7C5 21,24 12
Chromium on 1,2,5,6,17,21 3,7C5 3,7C5 3,7C5 3,7C5 5,6,9,10,20,21 5,6,9,10
nickel/nickel
Chromium on 1,2,5,6,17,21 3,7C5 3,7C5 3,7C5 3,7C5 5,6,9,10,20,21 5,6,9,10
nickel/copper
Cobalt 1,2,17  8,7B 9,10,12,21 9,10,12
Copper 1,5,17   10,12,20,21,24 10,12
Gold 3,7C1,7C2, 3,7C1,7C2, 3,7B,7C1,7C2, 3,7C1,7C2, 10,12,20,21,27 10,12
7C3,7C5,11, 7C3,7C5,11, 7C3,7C5,8,11, 7C3,7C5,
13A,13B,16, 13A,13B,16, 13A,13B,16, 11,13A,13B,
22A,23,25,26 22A,23,25,26 22A,23,24,25, 16,22A,23,
26 25,26
Indium   9,10,12 9,10,12
Lead   9,10,12,21,22 9,10,12
Nickel 1,2,17 11,25 7C6,11,25 1,7A,7B,10,11, 11,25 1,7C6,9,10,12, 9,10,12
25 20,21,24
Nickel-boron 1,2,17 11,25 11,25 8,11,25 11,25 9,10,12,20,21, 9,10,12
Nickel-cobalt 1,2,17 11 11 11 11
Nickel-iron 1,2,17 11 11 11 11
Nickel-phosphorus 1,2,17 11,25 11,25 8,11,25 11,25 9,10,12,20,21, 9,10,12
Palladium 3,7C1,7C2, 3,7A,7C1,7C2, 3,7B,7C1,7C2, 3,7C1,7C2,
7C3,7C5, 7C3,7C5,13A, 7C3,7C5,8,11, 7C3,7C5,
13A,13B,16,23 13B, 16,23 13A,13B, 16,23 13A,13B,16,
Phosphate conversion
Platinum 3,7C1,7C2, 3,7C1,7C2, 3,7C1,7C2,7C3, 3,7C1,7C2,
7C3,7C5 7C3,7C5 7C5 7C3,7C5
Rhodium 3,7C1,7C2, 3,7C1,7C2, 3,7C1,7C2,7C3, 3,7C1,7C2,
7C3,7C5,13A, 7C3,7C5,13A, 7C5,8,13A,13B 7C3,7C5,
13B 13B 13A,13B
Silver 7C2 7C2,14 7C2,14 7C2 9,10 9,10
Tin 19,22C,25 7C6,19,22C,2511,13B,19,22C, 19,22C,25 7C6,9,10,12,20, 9,10,12
25 21,22C,24
Tin-lead 22C 22C 11,13B,22C 22C 9,10,12,21,22C 9,10,12
Tin-nickel 19,22C,25 19,22C,25 13B,19,22C,25 19,22C,25 9,10,12,20,21, 9,10,12
22C,24
Tin-zinc 19 19 19 19 9 9
Zinc  7C6  4A,7C6,9,18 4A,9
Porcelain enamel   9,10,12 9,10,12
Organic films 4 11,25 11,25 11,25 11,25 9,10,12 9,10,12
NOTE Numbers refer to subclauses of Clause 7, and the letters to their variations.
12 © ISO 2006 – All rights reserved

ISO 10308:2006(E)
Table A.2 — Substrate or underlayer: magnesium alloys, nickel alloys, silver tin-nickel, zinc alloys
Substrate or underlayer
Coating
Nickel alloys
Magnesium Zinc
Silver Tin-nickel
alloys alloys
Nickel Nickel-boron Nickel-phosphorus
Aluminium
Anodized aluminium — — — — — — —
Brass
Cadmium   7C6
Chromate conversion 21   21
Chromium 2,7C7,15, 5  3,7C1 2,5,6,17,
17,21 21
Chromium on 2,7C7,15,   2,5,6,17,
nickel/nickel 17,21 21
Chromium on 2,7C7,15,   2,5,6,17,
nickel/copper 17,21 21
Cobalt 2,7C7,15,   2,17,21
17,21
Copper 7C7,15,17 7B   17
Gold 7C2,7C4,16,23 7C4,16,23 26
1,7A,7B, 7C2,7C4,16, 1,3,7A,7B,
7C2,7C4, 23 7C1,11,
13B,16,22A, 13A,13B,
23 22B,25
Indium
Lead
Nickel 2,7C7,15,17 — — — 7C6,11,25 2,17,21
Nickel-boron 2,7C7,15,17 — — — 11,25 2,17,21
Nickel-cobalt 2,7C7,15,17 — — —  2,17,21
Nickel-iron 2,7C7,15,17 — — — 11 2,17,21
Nickel-phosphorus 2,7C7,15,17  11,25 2,17
Palladium 7B,7C2,7C4, 7C2,7C4,13B, 7C2,7C4,13B,16, 23 3,7C1,11, 7C4,23
13B, 16, 23 16, 23 13A,13B
Phosphate conversion
Platinum 7C2,7C4 7C2,7C4 7C2,7C4 3,7C1 7C4
Rhodium 7C2,7C4, 7C2,7C4,13B 7C2,7C4,13B 3,7C1,13A, 7C4
13B 13B
Silver 7C2 7C2 7C2 —
Tin   7C6,11,
13B,25
Tin-lead   11,13B
Tin-nickel   13B,25 —
Tin-zinc
Zinc   7C6 —
Porcelain enamel
Organic films   25
NOTE Numbers refer to subclauses of Clause 7, and the letters to their variations.

ISO 10308:2006(E)
Annex B
(informative)
Typical report and evaluation of porosity tests
B.1 Report
The results of a porosity test are usually given in terms of one of the following.
B.1.1 Option 1
The number and size of the pores in the significant area. Convert to a pore density in number of defects per
100 mm .
B.1.2 Option 2
The percentage of total area covered by the pores.
B.1.3 Option 3
The area, in square millimetres, of the largest marking or spot on the significant surface.
B.2 Evaluation
B.2.1 Scope
Porosity tests offer some indication as to the expected performance of coating(s) when exposed to corrosive
environments. When a given coating of a specified thickness is known to be protective when properly
deposited, the porosity test(s) serve(s) as a meas
...