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.

Part 1 of the ISO/IEC Directive describes the procedures used to develop this document and for further maintenance. In particular, attention should be paid to the different approval criteria required for different types of ISO documents. This document has been drafted in accordance with the editorial rules of ISO/IEC Directive Part 2 (see iso.org/directives).

Please note that some elements of this document may be the subject of patent rights. ISO is not responsible for identifying any or all such patents. Details of any patent rights identified during the development of the document will be found in the introduction and/or list of ISO Patent declarations received (see iso.org/patents).

Any trade names used in this document are provided as information for the convenience of the user and do not constitute an endorsement.

ISO 22858-2020 – Electrochemical measurement of Corrosion of metals and alloys – Test method for monitoring atmospheric corrosion

Explanations of the relevant standards of voluntary, ISO specific terms related to conformity assessment and the expression of meaning, and the ISO in the technical barriers to trade (TBT) adhere to the principle of the world trade organization (WTO) information, please refer to the iso.org/iso/foreword.html.

This document has been prepared by the ISO/TC 156 Technical Committee on Corrosion of Metals and Alloys.

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.

introduce
The purpose of this document is to provide instructions on the use of electrochemical sensors to monitor atmospheric corrosion. These sensors are used for long-term measurement of thin film electrolyte conductance, corrosion current or coating condition. This method allows real-time assessment of corrosion currents associated with specific environmental conditions. Instantaneous corrosion current measurements cannot be obtained using resistance sensors or mass loss techniques. The techniques described in this document complement other standard techniques for assessing atmospheric corrosion, such as mass loss test sheets, resistance sensors or coating test plates (see ISO 8407 and ISO 4628-8). These continuous records of material conditions can be used to study atmospheric corrosion, evaluate materials, or manage assets. [21][22][23][24][25][26][27][28][29]

ISO 22858-2020 – Electrochemical measurement of Corrosion of metals and alloys – Test method for monitoring atmospheric corrosion

This document is based on ANSI/NACE TM0416-2016.

This document is relevant to alloy and coating manufacturers as well as users in transport, chemical process, energy and infrastructure applications.

1 Scope of Application
This document specifies a test method for atmospheric corrosion measurement using a two-electrode electrochemical sensor.

It is suitable for measuring the corrosion rate of uncoupled metal surfaces (i.e. the “free” corrosion rate), the galvanic corrosion rate, the conductivity of film solutions and the barrier properties of organic coatings. It specifies electrochemical sensors with or without the use of organic coatings. These sensors are suitable for corrosion measurements in laboratory test rooms, outdoor exposure sites and service environments.

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 4618, paints and varnishes – Terms and definitions

ISO 4628 (all parts), paints and varnishes – Assessment of coating degradation – designation of number and size of defects, and intensity of uniform changes in appearance

ISO 8044, Corrosion of metals and alloys – Vocabulary

ISO 22858-2020 – Electrochemical measurement of Corrosion of metals and alloys – Test method for monitoring atmospheric corrosion

ISO 9223, Corrosion of metals and alloys – corrosion of the atmosphere – classification, determination and estimation

3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4618, ISO 4628 (all parts), ISO 8044, ISO 9223 and the following apply.

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/

3.1 Resistance Sensor

A device for measuring corrosion, including measuring the ratio of an electric potential difference along a conductor to the current passing through it

Article Note 1: ISO 15091:2019, 3.1 defines “resistance” as “the ratio of the potential difference along a conductor to the current passing through it.”

ISO 22858-2020 – Electrochemical measurement of Corrosion of metals and alloys – Test method for monitoring atmospheric corrosion

3.2 Electrochemical Sensor

A device for measuring corrosion involving anode and cathode reactions

Note 1: ISO 8044:2020, 4.1 defines “electrochemical corrosion” as “corrosion involving at least one anode reaction and one cathode reaction”.

3.3 Number of Electrodes

Single finger of interdigital electrode (3.5)

3.4 Corrosion Penetration

The distance between the corroded surface and the original surface of the metal

Note 1: ISO 8044:2020, 3.11 defines “corrosion depth” as “the distance between a point on the surface of the metal affected by corrosion and the original surface of the metal”.

3.5 Interfinger electrodes

Electronic conductors that interlock like fingers

ISO 22858-2020 – Electrochemical measurement of Corrosion of metals and alloys – Test method for monitoring atmospheric corrosion

3.6 Sensor Range

Upper and lower limit measurements

3.7 Sensor Span

The difference between the maximum and minimum measurements

3.8 Solution resistance

The ratio of the electrode potential increment to the corresponding current increment depends on the solution

3.9 Film conductance

Current transfer capacity of solution layer

Article Note 1: ISO 15091:2019, 3.3 defines “conductance” as “the reciprocal of resistance”.

3.10 Zero-resistance ammeter

An instrument for measuring the current between two electrodes without potential drop

Only the standard information section is public. To see the full content, you need to purchase the standard through the official channels.