NF EN 12500

ISO 9223:2012 establishes a classification system for the corrosivity of atmospheric environments. It defines corrosivity categories for the atmospheric environments by the first-year corrosion rate of standard specimens, gives dose-response functions for normative estimation of the corrosivity category based on the calculated first-year corrosion loss of standard metals, and makes possible an informative estimation of the corrosivity category based on knowledge of the local environmental situation. ISO 9223:2012 specifies the key factors in the atmospheric corrosion of metals and alloys. These are the temperature-humidity complex, pollution by sulfur dioxide and airborne salinity. The temperature-humidity complex can be evaluated in terms of time of wetness. Corrosion effects of other pollutants (ozone, nitrogen oxides, particulates) are not considered decisive in the assessment of corrosivity according to ISO 9223:2012. ISO 9223:2012 does not characterize the corrosivity of specific service atmospheres, e.g. atmospheres in chemical or metallurgical industries.

ISO 9224:2012 specifies guiding values of corrosion attack for metals and alloys exposed to natural outdoor atmospheres for exposures greater than one year. It is intended to be used in conjunction with ISO 9223. Guiding corrosion values for standard structural materials can be used for engineering calculations. The guiding corrosion values specify the technical content of each of the individual corrosivity categories for these standard metals. ISO 9224:2012 provides examples of calculated maximum corrosion attack after extended exposure (up to 20 years) for six standardized corrosivity categories. It provides presumed average initial and steady-state corrosion rates of standard metals in intervals relative to six standardized corrosivity categories. It provides the calculation procedure for corrosion attack of steels in regard to their composition.

ISO 9225:2012 specifies methods for measuring the parameters needed for corrosivity estimation used for classification of the corrosivity of atmospheres in ISO 9223. ISO 9225:2012 specifies methods for the measurement of environmental parameters for normative corrosivity estimation based on calculated first-year corrosion rates of standard metals, and informative corrosivity estimation based on characterization of the exposure environment. It does not describe the usual analytical techniques for the measured parameters since this depends on the available analytical techniques used in laboratories. Specific methods for deposition measurement of SO2 and Cl- deposition rates and conversional factors for comparison of different measuring methods are given.

ISO 9226:2012 specifies methods which can be used for the determination of corrosion rate with standard specimens. The values obtained from the measurements (corrosion rates for the first year of exposure) are intended to be used as classification criteria for the evaluation of atmospheric corrosivity according to ISO 9223. They can also be used for informative evaluation of atmospheric corrosivity beyond the scope of ISO 9223.