BS EN ISO 15720:2001 – Metallic coatings — Porosity tests — Porosity in gold or palladium coatings on metal substrates by gel- bulk electrography
1 Scope
This test method covers equipment and techniques for determining porosity in noble metal coatings, particularly electrodeposits of gold, palladium and palladium-nickel alloy (70 % to 90 % palladium) and clad metals used on electrical contacts.
The gel-bulk procedure is not as sensitive to small pores and is more complex than porosity tests involving gaseous corrodants (see ISO 14647 and ISO 15721). It also involves more chemicals, preparation and auxiliary equipment.
This test is intended to be used for quantitative descriptions of porosity (such as number of pores per unit area or per contact) only on measurement areas where coatings have a sufficiently low pore density such that the corrosion sites are well separated and can be readily resolved. As a general guideline this can be achieved for pore densities up to about 25/cm 2 . Other porosity testing methods are outlined in ISO 10308. Detailed critical reviews of porosity testing are also available. Other porosity test methods are described in ISO 12687, ISO 14647 and ISO 15721.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards.
ISO 2064, Metallic and other inorganic coatings- Definitions and conventions concerning the measurement of thickness.
ISO 2079, Surface treatment and metallic coatings一- General classification of terms.
ISO 2080, Electroplating and related processes – Vocabulary.
ISO 10308, Metallic coatings一Review of porosity tests.
3 Terms and definitions
For the purposes of this International Standard, the terms and definitions given in ISO 2064, ISO 2079, ISO 2080 and ISO 10308 as well as the following apply.
3.1
decorations
coloured reaction products emanating from the pores that provide visual contrast with the gel medium NOTE While non-standard terms are deprecated, the term decorations has had long-standing use in differentiating between coloured pore indicators and true corrosion products. The term can be found in the technical literature.
3.2
metallic coatings
Includes platings, claddings, or other metallic layers applied to the substrate
NOTE The coatings can comprise a single metallic layer or a combination of metallic layers.
3.3
porosity
The presence of any discontinuity, crack, or hole in the coating that exposes a different underlying metal
4 Apparatus
4.1 Test vessel, of glass, acrylic resin or other inert colourless transparent material. It shall have thin-walled flat sides and be of a size appropriate to the sample to be tested.
BS EN ISO 15720:2001 – Metallic coatings — Porosity tests — Porosity in gold or palladium coatings on metal substrates by gel- bulk electrography