[h=2]Airborne Chlorides[/h]Airborne salinity refers to the content of gaseous and suspended salt in the atmosphere. It is measured by the concentration in the air in units of µg/m3. Since it is the salt that is deposited on the metal surface that affects the corrosion, it is often measured in terms of deposition rate in units of mg/m2/day. The chloride levels can also be measured in terms of the concentration of the dissolved salt in rain water.
A number of methods have been employed for determining the contamination of the atmosphere by aerosol transported chlorides, e.g. sea salt and road deicing salts. The ‘wet candle method,’ for example, is relatively simple, but has the disadvantage that it also collects particles of dry salt that might not be deposited otherwise. This technique uses a wet wick of a known diameter and surface area to measure aerosol deposition as shown in the following Figure.