ISO 15724:2001 金属およびその他の無機コーティング—鋼中の拡散性水素の電気化学的測定—フジツボ電極法 | ページ 2

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 3.

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 International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

International Standard ISO 15724 was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings, Subcommittee SC 2, Test methods.

Introduction

When atomic hydrogen enters steels and certain other alloys, it can cause loss of ductility or of load-carrying ability, cracking (usually submicroscopic cracks) or catastrophic brittle failure at applied stresses well below the yield strength or even the normal design strength of the alloys. This phenomenon often occurs in alloys that show no significant loss in ductility when measured by conventional tensile tests and is frequently referred to as"hydrogen-induced delayed brittle failure","hydrogen stress cracking" or"hydrogen embrittlement". The hydrogen can be introduced during fabrication, cleaning, pickling, phosphating, electroplating, autocatalytic processes and in the service environment as a result of cathodic protection reactions or corrosion reactions. Parts that have been machined, ground, cold-formed or cold-straightened subsequent to any heat treatment are especially susceptible to hydrogen embrittlement damage.

1 Scope

This International Standard describes a method that uses an electronic hydrogen detection instrument for measuring relative, diffusible hydrogen concentrations in bare steels or in plated steels after the coating has been removed. It is assumed that the hydrogen is uniformly distributed throughout a part.

The method does not measure actual hydrogen concentration. However, oxidation current densities measured against time provide a useful indication of relative hydrogen concentrations and, therefore, the measurements can be used for comparison purposes. The method may be used as a quality control procedure as it does provide a quick means of measuring the effectiveness of pre- and/or post-plating heat treatments or of monitoring hydrogen uptake during plating or due to corrosion.

It is important to note that the absence of failure in a particular test does not provide confirmation of complete elimination of hydrogen embrittlement because no one test method can provide all the data necessary to evaluate the degree of hydrogen degradation.

For unplated parts the method is non-destructive; however, for plated parts the coating has to be removed prior to measurement by a means proven not to damage the steel or to introduce hydrogen.

This test method is limited to:

• carbon and alloy steels, excluding austenitic stainless steels (see note 1);
• flat specimens to which the cell can be attached (see note 2);
• measurements at room temperature (25 °C ± 1 °C).

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.

Bibliography