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ISO 9223-2012 pdf free download
ISO 9223-2012 pdf free download.Corrosion of metals and alloys — Corrosivity of atmospheres — Classification, determination and estimation
Corrosion des métaux et ailiages — Corrosivife des atmospfleres — Classification, determination et estimation.
For unsheltered positions, the corrosion impact is mentioned in terms of dry and wet deposition. Wet deposition includes transport by means of precipitation and dry deposition denotes transport by any other process.
In sheltered positions, only dry deposition occurs. The cumulative effect of pollutants, including particulates, should be considered. Specific problems of atmospheric corrosivity of low aggressive indoor atmospheres are characterized in ISO 11844-1, ISO 11844-2 and ISO 11844-3.
The wetting of surfaces is caused by many factors, for example dew, rainfall, melting snow and a high humidity level. The length of time during which the relative humidity is greater than 80 % at a temperature greater than 0 °C is used to estimate the calculated time of wetness, r, of corroding surfaces. The time of wetness is underestimated by the time that the temperature exceeds 0 °C and 80 % RH in frigid zones (freezing point depression).
Information on calculated time of wetness is helpful for informative atmospheric corrosivity estimation. Table B. 1 presents time of wetness characteristics for different exposure conditions.
The most important factor within a particular temperature-humidity complex is the pollution level caused by sulfur dioxide or airborne salinity. The pollution level shall be measured in accordance with the specifications of ISO 9225.
Other kinds of pollution can also exert an effect [oxides of nitrogen (NOJ, nitric acid (HNO3) and industrial dust in populated and industrial zones] or the specific operational and technological pollution of microclimates [chlorine (Cl2), hydrogen sulfide (H2S). organic acids and de-icing agents]. These types of pollution have not been used as classification cnteria.
According to this International Standard, the other kinds of pollution should be considered as accompanying ones [e.g. oxides of nitrogen (NO1) in urban atmospheres] or specific operational ones (e.g. vapours of acids in operational microclimates), Concentrations of the most important pollutants in different atmospheric environments are listed in Table B.2.
The decreasing sulfur dioxide levels in many parts of the woild arid the elevated levels of nitrogen oxides caused by increasing traffic, together with ozone and particulates, has created a new multipollutant environmental situation. In other parts of the wo.ld. in relation to rapid development of industry, the corrosion effect of SO2 pollution is intensified and still dominating.
Atmospheric pollution considered for corrosivity dassification in the frame of this International Standard is divided into two groups: pollution by sulfur dioxide (SO2) and by airborne salinity. These two types of pollution are representative for rural, urban, industrial and marine atmospheres, The grouping of pollution by sulfur dioxide (SO2) for standard outdoor atmospheres is given in Table B.3.
Grouping of salinity in levels characteristic of types of atmospheres is given In Table B.4. It is necessary to consider the high importance of chloride accumulation on surfaces not washed by rain, especially in humid sites.ISO 9223-2012 pdf free download.
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