ISO 11844-1:2020

Overview - ISO 11844-1:2020 (Indoor Corrosivity Classification)

ISO 11844-1:2020, "Corrosion of metals and alloys - Classification of low corrosivity of indoor atmospheres - Part 1: Determination and estimation of indoor corrosivity," establishes a standardized approach for classifying low corrosivity indoor atmospheres. The standard defines corrosivity categories IC1 to IC5, specifies reference metals (five standard specimens, with lead added in the 2020 revision for high sensitivity to volatile organic acids), and describes how to determine or estimate indoor corrosivity that can affect metals and metallic coatings during storage, transport, installation or use.

Key Technical Topics and Requirements

• Classification framework: Subdivides ISO 9223’s broad outdoor corrosivity categories to provide a finer scale for low indoor corrosivity (IC1–IC5).
• Two assessment routes:
  • Determination by measuring corrosion attack on standard specimens after exposure (normally one year; shorter exposures such as one month permitted when conditions vary less than ±5%).
  • Estimation using environmental parameters (humidity, temperature, pollutants, air exchange) when direct exposure testing is not feasible.
• Reference metals and specimens: Uses corrosion attack (mass loss or mass increase) on selected metals to assign an indoor corrosivity category (details of specimen preparation and exposure methods are in ISO 11844-2).
• Environmental characterization: Identifies key indoor pollutants and microclimate factors that influence corrosivity - e.g., SO2, NO2, O3, H2S, Cl–, NH3, volatile organic acids (formic, acetic), aldehydes, particles, relative humidity and time-of-wetness.
• Indoor/outdoor model: Includes a steady-state I/O model linking indoor pollutant concentrations to outdoor levels via air-exchange rate, deposition velocity and room surface-to-volume ratio.
• Recommendation: Direct measurement of corrosion attack is strongly recommended over estimation when possible.

Practical Applications and Users

ISO 11844-1 is practical for organizations needing reliable indoor corrosivity data:

• Conservation professionals and museums - assess risk to works of art and historic metal objects.
• Electronics and precision equipment manufacturers - specify storage and packaging environments to prevent corrosion-related failures.
• Materials and corrosion engineers - design coatings and select materials for indoor service conditions.
• Facility managers, HVAC and building engineers - control indoor air quality, ventilation and filtration to reduce corrosivity.
• Storage, logistics and archival services - evaluate environments for long-term preservation of metal-containing items.

Related Standards

• ISO 11844-2 - methods, specimen descriptions and evaluation for measuring corrosion attack.
• ISO 11844-3 - measurement methods for environmental parameters affecting indoor corrosivity.
• ISO 9223 - general atmospheric corrosivity classification.
• ISO 16000 series - guidance for indoor air sampling and pollutant identification.

Using ISO 11844-1:2020 helps stakeholders quantify and manage indoor corrosivity risks to protect metals, prolong service life, and support preventive maintenance and conservation strategies.