ISO 9225 pdf download – orrosion of metals and alloys -Corrosivity of atmospheres -Measurement of environmental parameters affecting corrosivity of atmospheres.
Contaminants other than SO2 and Cl-, such as NO,. 03, H2S. HNO3, can also exert an effect on the corrosion rate Corrosion active components of dust deposits (SO42- NO3. Cl) react with metals in the presence of humidity. These factors are considered as accompanying factors (see ISO 9223). These environmental parameters. wtiicti contribute to the effect on coirosion of standard metals in multi-pollutant situations, are not included as rnandalory parameters for corrosivity estimation ii ISO 9223, Information on levels of these parameters can help in informative corrosivity estimation.
Methods for the measurement of environmental parameters to be used specifically for the estimation of low corrosivity of indoor atmospheres (IC) are given in ISO 11 8443.
4 Humidity and temperature parameters
4.1 RelatIve humIdIty
Reliable long-term average values for relative humidity can often be obtained from the meteorological authorities in the country. Several types of measuring devices can be used if collection of new data for the locality is needed There are several continuous measuring devices, such as hygrograpils. thermohyographs or logging hygrometers, available on the market.
The period of measurement is preferably one year irs order to cover seasonal vanations and because the ctassificabon system is based on yearly average values. The data shall be expressed as yearly mean values.
4.2 Temperature
Reliable long-term average values for temperature can often be obtained from the meteorological aulhonties in the country. Several types of measuring devices can be used if collection of new data for the locality Is needed. There are several continuous measuring devices, such as thermohygrographs or logging thermometers, available on the market.
The period of measurement is preferably one year in order to cover seasonal variations and because the classification system is based on yearly average values The data shall be expressed as yearly mean values.
5 Airborne contaminants
5.1 PrInciple
The gas concentration or deposition rate may be measured using several techniques:
— continuous gas concentration measuring instruments:
average gas concentration witt active sampler and air pump:
— average gas concentration with diffusive (passive) sampler:
— average deposition rate equipment
The results from concentration measurements are typically given ii micrograms per cubic metre (pg!m3) and. for deposition measurements. In milligrams per square metre per clay.
5.2.2 Measurement instruments with active sampler
The active sampler equipment shall be placed according to the same rules as the continuous gas-measuring
Instrument.
5.2.3 Measurement Instruments with diffusive sampler
The sampling device shall be placed with the open end facing downward under appropriate sheller. The air flow influences the gas diffusion in the sampler.
5.2.4 Deposition rate equipment
The equipment shall be sheltered from setting particles and from washing out by rain for outdoor deposition
measurements. The air flow influences the deposition rate.
5.3 Measurement methods and duration
5.3.1 Continuous measurement
The measurements shall preferably be carried out for one year in order to record the seasonal variation of the gas pollutants. The data from continuous measuring instruments shall be recorded as monthly average values For the corrosivity estimation, the data shall be expressed as yearly mean values.
Standard instruments have detection Irlits in a range from 4 10 volume fractions to 1 “10 6 volume fractions.
5.3.2 Measurement with activ, sampler
The methods are based on pumping air through an absorption unit with a reactive surface or liquid, with subsequent laboratory analysis of the amount absoibed The sampling period shall be one week, The data shall be collected over the sampling periods and summarized to monthly average values. The result is given as an average concentration for the measuring period.
The measuring period is peferably one year or at least one month for each season of the year. For the corrossvlty estimation, the data shall be expressed as yearly mean vakies
NOTE The detection limits for air concenlrationa depend on the sensitMty of the analysing rns*ruments aid the duration of the sampling. For an analytical instrument with normal sensitrvity, Ills possible to obtain weelcly average values with a detection Imit better than 0.1 pgtin.
5.3.3 Measurement with diffusive sampler
Mean gas concentrations can be calculated using diffusive sampkng devices, The principle used for diffusive sampling is shown in Figure 1. The recommended sampling period is one month, but can be extended to three months, corresponding to one measurement for each season of the year The measurement period is preferably one year.
ISO 9225 pdf download – Corrosion of metals and alloys -Corrosivity of atmospheres -Measurement of environmental parameters affecting corrosivity of atmospheres
