preface
ISO (International Organization for Standardization) is a global alliance of national standards bodies (ISO member bodies). The development of international standards is usually carried out through ISO technical committees. Each member institution interested in a subject on which a technical committee has been established has the right to be represented on that committee. International governmental and non-governmental organizations liaising with ISO are also involved in this work. ISO works closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International standards are drafted in accordance with the rules given in Part 2 of the ISO/IEC Directive.

The main task of the technical committee is to set international standards. The draft international standards adopted by the Technical Committee will be circulated to member bodies for voting. Publication as an international standard requires approval by at least 75% of member bodies.

Please note that certain contents of this document may be subject to patent rights. ISO is not responsible for identifying any or all such patents.

ISO 21227-4 was prepared by the Technical Committee Subcommittee ISO/TC 35 (Paints and varnishes), SC 9 (General test methods for paints and varnishes) in cooperation with the Technical Committee CEN/TC 139 (Paints and Varnishes).

ISO 21227 consists of the following parts under the general heading Paints and Varnishes – Assessment of Defects on coated Surfaces Using optical Imaging:

— Part 1: General guidance

— Part 2: Evaluation procedure for multiple impact lithotripsy tests

— Part 3: Assessment of delamination and corrosion around lines

— Part 4: Evaluation of filamentous corrosion

ISO 21227-4-2008 Paints and varnishes – Assessment of defects on coated surfaces using optical imaging – Part 4: Assessment of filamentous corrosion

introduce
Traditional ISO testing methods used to assess surface defects and appearance changes typically use graphic standards that depict specific types of surface deterioration and require human visual evaluation. Compared with human visual assessment techniques, the techniques described in the various sections of this standard can produce more objective, accurate, quantitative and repeatable results.

1 range
This section of ISO 21227 describes a method for evaluating filamentous corrosion by digital optical imaging. Filamentous corrosion may be performed according to ISO 4623-1, ISO 4623-2 or EN 3665.

2 Normative references

The following references are required for the use of this document. For dated references, citation-only versions apply. For undated references, the latest version of the reference (including any revisions) applies.

ISO 4623-1, Paints and varnishes – Determination of filamentous corrosion – Part 1: Steel substrates

ISO 4623-2, Paints and varnishes – Determination of filamentous corrosivity – Part 2: Aluminium substrates

ISO 21227-1, Paints and varnishes – Assessment of defects on coated surfaces using optical imaging – Part 1: General guidance

Aerospace series – Paints and varnishes – Test methods – Filament resistance to corrosion of aluminium alloys – EN 3665

3 Terms and Definitions
For the purposes of this document, the terms and definitions set forth in ISO 21227-1 and below apply.

3.1 Filamentary corrosion

Type of corrosion in the form of filaments under paint, varnish, or a related product coating, usually starting with a bare edge or local damage to the coating

Note 1: Usually, filaments are irregular in length and direction of growth, but they may also be almost parallel and roughly equal in length.

Note 2 Filamentous corrosion may also occur under other protective coatings.

[Source: ISO 4623-1]

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