ISO 8502-9:2020 塗料および関連製品を塗布する前の鋼基板の準備—表面の清浄度を評価するためのテスト—パート9：水溶性塩の導電率測定のための現場法 | ページ 2

Foreword

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The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, 2 (see www.iso.org/directives ).

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This document was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee SC 12, Preparation of steel substrates before application of paints and related products, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 139, Paints and varnishes, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This second edition cancels and replaces the first edition (ISO 8502-9:1998), which has been technically revised.

The main changes compared to the previous edition are as follows:

—inclusion of new measurement methods according to the direct sample method;

—improved connection to ISO 8502-6, and all extraction types;

—dedication to water soluble salts to avoid confusion with other analysis methods;

—improvement to Figure 1 to clarify the use of other volumes for analysis.

A list of all parts in the ISO 8502 series can be found on the ISO website.

Introduction

The performance of protective coatings of paint and related products applied to steel is significantly affected by the state of the steel surface immediately prior to painting. The principal factors that are known to influence this performance are:

• a) the presence of rust and mill scale;
• b) the presence of surface contaminants, including salts, dust, oils and greases; and
• c) the surface profiles.

ISO 8501, ISO 8502 and ISO 8503 have been prepared to provide methods of assessing these factors, while ISO 8504 provides guidance on the preparation methods that are available for cleaning steel substrates, indicating the capabilities of each in attaining specified levels of cleanliness.

These International Standards do not contain recommendations for the protective coating systems to be applied to the steel surface. Neither do they contain recommendations for the surface quality requirements for specific situations even though surface quality can have a direct influence on the choice of protective coating to be applied and on its performance. Such recommendations are found in other documents such as national standards and codes of practice. It is be necessary for the users of these International Standards to ensure that the qualities specified are:

• compatible and appropriate both for the environmental conditions to which the steel is exposed and for the protective coating system to be used, and
• within the capability of the cleaning procedure specified.

The four International Standards referred to above deal with the following aspects of preparation of steel substrates before application of paints and related products:

• ISO 8501, Visual assessment of surface cleanliness;
• ISO 8502, Tests for the assessment of surface cleanliness;
• ISO 8503, Surface roughness characteristics of blast-cleaned steel substrates;
• ISO 8504, Surface preparation methods.

Each of these International Standards is in turn divided into separate parts.

This document describes a field method for the assessment of the total amount of water-soluble salts, the salts being reported as one value. The more aggressive contaminants causing corrosion and blistering (the ionic species) can easily be dissolved off and determined by this method. Consequently, the less aggressive and not so easily dissolved minor part of contaminant remains un-assessed. For additional information on the test method, its potential and its limitations, see Bresle Å, Conductometric determination of salts on steel surfaces^[1] and Frankhuizen N, Measuring NaCl, Salt and Soluble Contaminants with Bresle Patches — 1 & 2^[2].

Rusty steel substrates, particularly those of rust grades C or D (see ISO 8501-1), even when blast-cleaned to preparation grade Sa 3 (see ISO 8501-1 and ISO 8501-2), might still be contaminated by water-soluble salts and corrosion products. These compounds are almost colourless and are localized at the lowest point of the rust pits. If they are not removed prior to painting, chemical reactions can result in blister formation and accumulations of rust that destroy the adhesion between the substrate and the applied protective coating.

Even if the salt is readily soluble in water, it is often impossible to remove it completely from the surface by a simple washing or extracting. The method described does not, therefore, determine the total amount of soluble materials on the surface but gives an indication of the cleanliness level of the surface. Prolonging the extractions time, or repeating the extraction procedure, should remove a larger proportion of the salt.

1 Scope

This document specifies a field method for the assessment of the surface density of various water-soluble salts on steel surfaces, before and/or after surface preparation, by conductometric determination. The individual surface densities of the salt composition like chlorides, sulphates, sodium, etc, cannot be determined by this method.

This method assesses only contaminants that forms an electrolyte (ions) when in contact with water. These represent the greater part of the contaminants.

2 Normative references

The following documents are referred to in the text in such a way that some or all their content constitutes requirements 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.

3 Terms and definitions

No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

Bibliography