ISO 22858:2020

Overview

ISO 22858:2020 - "Corrosion of metals and alloys - Electrochemical measurements - Test method for monitoring atmospheric corrosion" defines a standardized test method using two-electrode electrochemical sensors to monitor atmospheric corrosion. The standard covers measurement of the free (uncoupled) corrosion rate, galvanic corrosion rate, conductance of thin film solutions, and barrier properties of organic coatings. Sensors described can be used with or without coatings, and are suitable for laboratory test chambers, outdoor exposure sites and in-service environments.

Key topics and requirements

• Sensor types and geometry
  • Free corrosion current sensors
  • Galvanic corrosion current sensors
  • Thin-film conductance sensors
  • Coating barrier property sensors
• Measurement methods
  • Free corrosion: sine-wave, triangle-wave and potential-step excitation methods for uniform corrosion; procedures for localized corrosion
  • Galvanic corrosion: zero-resistance ammeter and precision-resistor methods
  • Surface conductance and coating barrier measurements using two-electrode techniques
• Output metrics
  • Corrosion current and current density, corrosion penetration and mass loss rates, total charge for coated sensors, and conductance of thin films
• Preparation and verification
  • Surface preparation considerations for sensors with and without coatings
  • Specification and inspection requirements: visual checks, span/range verification, electrical tests and corrosion verification tests
• Test execution and reporting
  • Guidance on atmospheric test types, test arrangement, sampling intervals, duration, sensor selection and data storage
  • Test report content and example reporting information
• Supporting information
  • Informative annexes with example sensor images, equivalent circuit analysis for two-electrode measurements, reporting examples and bibliography

Applications

ISO 22858:2020 is designed for real-time, continuous monitoring of atmospheric corrosion where instantaneous electrochemical data are required. Practical applications include:

• Evaluating corrosion performance of metals and alloys in atmospheric exposure testing
• Assessing galvanic interactions between dissimilar materials
• Monitoring thin-film electrolyte conductance (e.g., salt films, condensation)
• Testing coating barrier performance and early detection of coating breakdown
• Laboratory R&D, outdoor exposure sites, plant/infrastructure asset condition monitoring and life‑cycle assessment

Who should use this standard

• Corrosion engineers and materials scientists
• Coatings manufacturers and test laboratories
• Asset managers responsible for infrastructure and industrial equipment
• Researchers conducting environmental exposure and corrosion studies

Related standards

• ISO 8407 (mass loss corrosion testing methods)
• ISO 4628-8 (evaluation of degradation of coatings) These standards complement ISO 22858 when combining electrochemical monitoring with mass-loss or visual coating assessment.

Keywords: ISO 22858:2020, atmospheric corrosion, electrochemical measurements, corrosion sensors, galvanic corrosion, free corrosion current, thin-film conductance, coating barrier properties.