Atmospheric environment classification

ISO CORRAG [23], the International Organization for Standardization (ISO) has implemented a classification system for evaluating atmospheric corrosivity and on the basis of variables that are fairly easy to obtain [24, 25]. This ISO classification has found several applications, for example, to predict the long-term corrosion behavior in different environments and to evaluate the effect of protective coatings. It contains two principally different approaches of assessing the corrosivity of any outdoor atmospheric environment. The first is based on exposure of standard specimens of steel, copper, zinc, and aluminum for one year whereby the corrosion effect is measured through mass loss measurements. One of five measured corrosivity classes... 

The classification given in Table 1.2 is based on the various forms that corrosion may take, but the terminology used in describing corrosion phenomena frequently places emphasis on the environment or cause of attack rather than the form of attack. Thus the broad classification of corrosion reactions into wet or dry is now generally accepted, and the nature of the process is frequently made more specific by the use of an adjective that indicates type or environment, e.g. concentration—cell corrosion, crevice corrosion, bimetallic corrosion and atmospheric corrosion. 

In a sense this subdivision of the composition of the atmosphere is arbitrary since some of the so-called contaminants are derived partly or wholly from natural sources. However, in that their concentrations vary appreciably within very narrow geographical limits, they may be distinguished from the contents of Table 2.8 (with the possible exception of water vapour). Table 2.6 lists those contaminants which are important from a corrosion standpoint. Excluded are contaminants found only in very specific locations, e.g. in the vicinity of a chemical works. The concentrations given are intended only to indicate general levels in the usual classification of environments and not to define a particular environment. 

Estimated releases of 2 poimds (0.9 kg) of 3,3 -dichlorobenzidine to the atmosphere from one facility in 1996, accoimted for 100% of the estimated total environment releases (TR196 1998). These releases are summarized in Table 5-1. The TRl data should be used with caution because only certain types of facilities are required to report information to the Toxics Release Inventory only if they employ more than 10 full-time employees, if their facility is classified rmder Standard Industrial Classification (SIC) codes 20 through 39, and if their facility produces, imports, or processes 25,000 or more pounds of any TRl chemical or otherwise used more than 10,000 pounds of a TRl chemical in a calendar year (EPA 1997). 

The section on metallic corrosion clearly indicates that the conventional method of classification of environments into marine, industrial, and rural no longer is adequate. More specific information is needed about the actual chemical components in the atmosphere as well as humidity and other factors. Specific environments also are addressed in the metallic corrosion section. For example, the automotive environment in the northeastern United States is particularly severe because of the combination of acid deposition and the use of road de-icing salts. These factors exert a synergistic effect on the corrosion behavior of auto-body steel and on exterior anodized aluminum automobile trim. 

Data for the former Soviet Union and other parts of Eastern Europe are not readily available in English. Fuller details follow, based on a selection made by Dr. E. Proskurkin, who has primarily selected data from contributions in two books (Rosenfeld, 1%0 Berukshtis and Klark, 1971), plus other selected reports. The Russian Institute of Physical Chemistry, which has been responsible for much of the work of these investigators, has amplified (Table 2.19) the brief classification of environments given in Table 2.1. Mikhailovskii et al. (1986) have developed mathematical expressions for the corrosion of metals. These expressions differ according to whether the atmosphere is coastal or industrial. Note For the convenience of Western readers, the symbols used here are different from those in the original paper.)... 

Other areas discussed include the classification of pesticides by degree of toxicity and danger, the system of research and regulation in the USSR, and the principle of integrated standardization of pesticide content of food, water, and atmospheric air. The review concludes with a look at certain prospective trends in the search for and development of pesticides that have selective action on target organisms but are harmless to human health and the environment. 

According to European parliament regulation 1005/2009, the use of any solvent with the H420 (harms public health and the environment by destroying ozone in the upper atmosphere) hazard phrase in the Globally Harmonized System (GHS) of Classification and Labelling of Chemicals is severely restricted. 

While it is generally important to rank macro-level environments according to a normalized corrosivity classification, specific information about atmospheric corrosivity and corrosion rates is often required on the micro level. For example, a corrosion risk assessment may be required for a military aircraft operating out of a specific air base environment. One such requirement resulted in a report of the... 

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