ISO 11844-2:2020

Overview

ISO 11844-2:2020 - Corrosion of metals and alloys: Classification of low corrosivity of indoor atmospheres - Part 2 - specifies practical, standardized methods to determine corrosion attack on metals and alloys in indoor environments of low corrosivity. It defines direct measurement techniques using standard specimens (copper, silver, zinc, carbon steel and lead) and translates measured corrosion rates into classification criteria for indoor atmospheric corrosivity.

Key topics and technical requirements

• Specified test specimens: flat rectangular specimens (recommended 10 mm × 50 mm, ~0.5 mm thick) of defined material purities (e.g., Ag 99.98 %, Cu 99.85 %, Pb 99.97 %).
• Specimen preparation: controlled abrading, cleaning (de-ionized water), ultrasonic degreasing in ethanol, drying and sealed storage to avoid contamination.
• Exposure arrangements: vertical mounting with free air circulation; sheltered and unsheltered racks are illustrated; recommended mounting height ~1 m above floor and minimum spacing from supports to allow airflow.
• Measurement methods:
  • Mass change measurements (Annex A) - mass increase or mass loss determined by micro-balance (weighing procedure relative to a reference standard). Exposure typically 6 months to 1 year. Pickling and blank controls are used for mass-loss evaluations.
  • Electrolytic cathodic reduction (Annex B) - used mainly for silver and copper to determine film thickness or mass loss; interpretation considers corrosion-product chemistry.
  • Resistance measurements (Annex C) and quartz crystal microbalance (QCM) (Annex D) - suitable for continuous or periodic monitoring and higher sensitivity.
• Accuracy and precision: micro-balance accuracy (±0.1 mg) and method precision estimates are provided to support classification decisions.
• Use of results: measured corrosion rates (mass or resistance changes normalized by area and exposure time) are used as classification criteria to assign indoor corrosivity categories.

Applications and who should use it

ISO 11844-2:2020 is relevant for:

• Corrosion engineers and testing laboratories performing indoor-corrosivity assessments.
• Facilities and asset managers responsible for control rooms, electrical enclosures, storage rooms, transport containers, and electronic equipment protection.
• Museum conservators and cultural heritage professionals assessing risks to metal artifacts and showcases.
• Electronics and component manufacturers validating environmental suitability and warranty claims.
• Standards and compliance teams that need objective, repeatable data to classify indoor atmospheres and design mitigation (filtration, coatings, material selection).

Practical benefits include objective, repeatable corrosion-rate data to guide material choices, environmental controls, storage policies, and maintenance schedules.

Related standards

• Other parts of the ISO 11844 series (for complementary guidance on classification and sampling).
• ISO 8407 (cleaning and pickling procedures referenced for mass-loss determination).
• Work developed by ISO/TC 156 (Corrosion of metals and alloys).

Keywords: ISO 11844-2:2020, corrosion of metals, indoor atmospheres, low corrosivity, corrosion rate determination, mass change, electrolytic cathodic reduction, quartz crystal microbalance, corrosion monitoring, copper, silver, zinc, steel, lead.