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

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ISO 8502-9-2020 Preparation of steel substrates before painting and associated products – Tests for assessment of surface cleanliness – Part 9: Field method for determination of electrical conductance of water-soluble salts

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This document by 35 technical committee ISO/TC, paints and varnishes, subcommittee SC 12, the preparation of coatings and related products before application of the steel substrate, and the European committee for standardization (CEN) technical committee CEN/TC 139 cooperative writing, paint and varnish, In accordance with the Technical Cooperation Agreement between ISO and CEN (Vienna Agreement).

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

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

– Incorporating new measurement methods based on direct sampling;

– Improved connectivity to ISO 8502-6 and all extraction types;

– Focus on water-soluble salts to avoid confusion with other analytical methods;

– Improve Figure 1 to clarify analysis using other volumes.

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

Any feedback or questions on this document should be referred to the user’s national standards body. A complete list of these institutions can be found at iso.org/members.html.

ISO 8502-9-2020 Preparation of steel substrates before painting and associated products – Tests for assessment of surface cleanliness – Part 9: Field method for determination of electrical conductance of water-soluble salts

introduce
The performance of protective coatings applied to steel paints and related products is significantly affected by the state of the steel surface prior to coating. The main factors known to affect this performance are:

a) The presence of rust and oxide;

b) the presence of surface contaminants, including salt, dust, oil and grease; and

c) Surface profile.

ISO 8501, ISO 8502 and ISO 8503 are ready to provide methods for assessing these factors, while ISO 8504 provides guidance on preparation methods that can be used to clean steel substrates, indicating the ability of each method to achieve a specific level of cleanliness.

These international standards do not contain recommendations for protective coating systems for steel surfaces. They also do not contain recommendations for surface quality requirements for specific situations, although surface quality can directly affect the choice of protective coating to be applied and its performance. Such recommendations can be found in other documents, such as national standards and codes of practice. Users of these international standards need to ensure that the specified quality is:

– Compatible with and suitable for the environmental conditions to which the steel is exposed and the protective coating system to be used, and

– Within the capacity of the prescribed cleaning procedures.

ISO 8502-9-2020 Preparation of steel substrates before painting and associated products – Tests for assessment of surface cleanliness – Part 9: Field method for determination of electrical conductance of water-soluble salts

The above four international standards cover the following preparation of steel substrates prior to the application of paints and related products:

– ISO 8501, visual assessment of surface cleanliness;

– ISO 8502, surface cleanliness assessment test;

– ISO 8503, surface roughness characteristics of sandblasting steel substrates;

– ISO 8504, surface treatment methods.

Each of these international standards is divided into separate sections.

The document describes an on-site method for assessing the total amount of water-soluble salts that are reported as one value. The more aggressive contaminants (ionic substances) that cause corrosion and foaming can be easily dissolved and determined by this method. As a result, small amounts of pollutants that are less aggressive and less soluble remain unassessed. For more information on test methods, their potential and limitations, see Bresle A, Conductivity determination of salts on steel surfaces [1] and Frankhuizen N, Measurement of NaCl, salts and soluble contaminants using Bresle Patches – Part 1 and Part 2 [2].

Rusted steel substrates, especially those with rust grades C or D (see ISO 8501-1), may still be contaminated with water contamination – soluble salts and corrosion products – even after sandblasting to preparation grades Sa 3 (see ISO 8501-1 and ISO 8501-2). These compounds are almost colorless and are located at the lowest point of the rust pit. If they are not removed before painting, chemical reactions can cause blistering and rust buildup, which breaks the adhesion between the substrate and the protective coating applied.

ISO 8502-9-2020 Preparation of steel substrates before painting and associated products – Tests for assessment of surface cleanliness – Part 9: Field method for determination of electrical conductance of water-soluble salts

Even though salt is easily soluble in water, it is usually not possible to completely remove it from the surface by simple washing or extraction. Therefore, the method described cannot determine the total amount of soluble material on the surface, but can indicate the level of cleanliness of the surface. Extending the extraction time, or repeating the extraction process, should remove a greater proportion of the salt.

1 Scope of Application
This document specifies a field method for assessing the surface density of various water-soluble salts on steel surfaces by conductivity determination before and/or after surface treatment. The individual surface densities of salt components such as chloride, sulfate, sodium, etc., cannot be determined by this method.

This method only assesses contaminants that form electrolytes (ions) when in contact with water. These represent the majority of pollutants.

2 Normative reference documents

When the following documents are referenced in the text, some or all of them constitute the requirements of this document. For dated references, only the cited version applies. For undated citations, a new version of the referenced document (including any revisions) applies.

ISO 3696, Analytical laboratory water use – specifications and test methods

ISO 8502-6, Preparation of steel substrates before painting and related products – Tests for assessment of surface cleanliness – Part 6: Extraction of soluble contaminants for analysis using adhesion pools – Bresle method

ISO 8502-9-2020 Preparation of steel substrates before painting and associated products – Tests for assessment of surface cleanliness – Part 9: Field method for determination of electrical conductance of water-soluble salts

3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminology databases for standardization at the following addresses:

– ISO online browsing platform: iso.org/obp

– IEC Electropedia: available at electropedia.org

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