ISO/TC 156/WG 4 - Atmospheric corrosion testing and classification of corrosivity of atmosphere

This document gives guidelines for producing corrosivity maps and maps related to increased risk of corrosion in outdoor open atmospheres, but not sheltered or semi-sheltered positions. The maps are calculated based on environmental data using specific relationships, so-called dose-response functions. Other means of producing corrosivity maps, for example using detailed measurements of corrosion and subsequent interpolation of measured corrosion values, are not within the scope of this document.

This document specifies a method for evaluating the aesthetic appearance of stainless steels qualitatively by rating rust and stains formed by atmospheric corrosion. The rust and stains on stainless steels formed by atmospheric corrosion are rated by using 10 photographic standards. This method is especially suitable for evaluating the appearance of specimens and structures made of stainless steels under atmosphere exposure.

This document specifies methods for determining corrosion rates with standard specimens of metals in indoor atmospheres with low corrosivity. For this direct method of evaluation corrosivity, different sensitive methods can be applied using standard specimens of the following metals: copper, silver, zinc, steel and lead. The values obtained from the measurements are used as classification criteria for the determination of indoor atmospheric corrosivity.

This document establishes a classification of low corrosivity of indoor atmospheres. It specifies the reference metals for which a corrosion attack after a defined exposure period is used for determining corrosivity categories of indoor atmospheres of low corrosivity. It defines corrosivity categories of indoor atmospheres according to corrosion attack on standard specimens. It indicates important parameters of indoor atmospheres that can serve as a basis for an estimation of indoor corrosivity. The selection of a method for the determination of corrosion attack, description of standard specimens, exposure conditions and evaluation are given in ISO 11844-2. The measurement of environmental parameters affecting indoor corrosivity is given in ISO 11844-3.

This document specifies methods for measuring the environmental parameters used to classify the corrosivity of indoor atmospheres on metals and alloys.

ISO 7441:2015 specifies and compares methods for the determination of bimetallic corrosion of metals and coated metals in atmospheric exposure corrosion tests. The methods are intended for the determination of the amount and type of corrosion effect, arising in natural atmospheres, caused by contact with different metals.

This International Standard specifies procedures to determine and estimate runoff rates of metals from metals, alloys and coatings under atmospheric conditions carried out in the open air.

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.

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 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 8565:2011 establishes general requirements for stationary corrosion testing of metals and metallic and other inorganic coatings under atmospheric conditions carried out in the open air or under shelters. It can also be applied for testing of complex specimens and assemblies of metallic materials.

ISO 11303 gives guidance on the selection of methods of protection against atmospheric corrosion of metals and alloys. It is applicable for technical equipment and products made of structural metals and used under atmospheric conditions. In a rational selection of protection methods, the corrosivity of the atmospheric environments is one of the important factors. These guidelines use the atmospheric corrosivity classification defined in ISO 9223.

ISO 11844-3:2006 describes methods for measuring the environmental parameters used to classify the corrosivity of indoor atmospheres on metals and alloys.

ISO11844-1:2006 deals with the classification of low corrosivity of indoor atmospheres. The aim of ISO11844-1:2006 is to characterise indoor atmospheric environments of low corrosivity that can affect metals and metallic coatings during storage, transport, installation or operational use, to set a consistent way of indoor corrosivity classification, and to prescribe procedures for derivation and estimation of indoor corrosivity categories. ISO11844-1:2006 specifies technical metals, whose corrosion attack after a defined exposure period is used for determination of corrosivity categories of indoor atmospheres of low corrosivity. ISO11844-1:2006 defines corrosivity categories of indoor atmospheres according to corrosion attack on standard specimens. ISO11844-1:2006 indicates important parameters of indoor atmospheres that can serve as a basis for an estimation of indoor corrosivity.

ISO 11844-2:2005 specifies methods for determination of corrosion rate with standard specimens of metals in indoor atmospheres with low corrosivity. For this direct method of evaluation of corrosivity, different sensitive methods can be applied using standard specimens of the following metals: copper, silver, zinc and steel. The values obtained from the measurements are used as classification criteria for the determination of indoor atmospheric corrosivity.

Specifies the principle, the standard specimens, the exposure of standard specimens and the expression of results. Figure 1 shows an open helix specimen assembly. Gives chemical cleaning procedures for removal of corrosion products (informative Annex A).

Specifies the three key factors in the atmospheric corrosion that are: the time of wetness, pollution by sulfur dioxide, air-borne salinity. Defines 5 categories of corrosivity of the atmosphere. Gives terms and definitions.

Specifies three methods for measuring the deposition rates of sulfur dioxide and air-borne salinity. Does not cover concentration measurements. Includes measuring methods which apply for characterization of corrosivity of the test site.

Specifies guiding corrosion values and characteristics of corrosion for the corrosion categories defined in ISO 9223. Gives terms and definitions.

Describes requirements for test specimens, test sites and their characterization, operating conditions, test procedures and the test report.

Applies to metals and alloys, and metals and alloys with metallic and non-metallic non-organic coatings. The methods are intended for the determination of the amount and type of corrosion effect, arising in natural atmospheres, caused by contact with different metals (coated metals), and for the evaluation of the effectiveness of bimetallic corrosion protection treatments.