Weathering atmospheric pollutants

Open Tanks These may be used to store materials that will not be harmed by water, weather, or atmospheric pollution. Otherwise, a roof, either fixed or floating, is required. Fixed roofs are usually either domed or coned. Large tanks have coned roofs with intermediate supports. Since negligible pressure is involved, snow and wind are the principal design loads. Local building codes often give required values. 

While the continual removal of atmospheric pollution by rain washing is beneficial, the removal of the protective corrosion product is obviously undesirable. The retention of the weathered surface is therefore usually preferred unless aesthetic considerations are of major importance, in which case abrasive or specialist chemical cleaning are effective. 

It has long been recognized that local environmental characteristics influence the rates of material corrosion. After two years of measurements at 39 sites in Europe and North America, significant relationships have been shown between corrosion rates of building materials and atmospheric pollutants( 5). While direction of exposure relative to weather and other factors such as frequency and duration of wetting significantly influence corrosion, Kucera (46) has shown that sulphur oxides are strongly correlated with deterioration of structural materials. 

Sculptures and architectural structures and ornaments constitute another category of metallic heritage to be conserved. Their unique character within the broader conservation framework is defined by the considerable range of metals and finishes, sizes, and functions. Moreover, an outdoor location demands treatment that will withstand wind, weather, traffic vibrations, and atmospheric pollution. Most of the objects are also accessible to public touch and vandalism. 

Inorganic constituents are present in major, minor, and trace concentrations in aquatic environments as a result of weathering, atmospheric, and biogeochemical processes, and also as a consequence of industrial pollution. Inorganic constituents in aquatic ecosystems are a group of chemical species that are characterized by... 

Among the possibilities are the effect of the weather and atmospheric pollution on the properties of the exposed surfaces of components. They will become roughened and will adsorb increasing amounts of moisture and conductive impurities. Surface discharges may occur which will result in further deterioration due to local high temperatures and the sputtering of metallic impurities from attached conductors. 

Kennedy et al. (2002) applied strontium isotopes to differentiate between weathering and atmospherically derived sources of strontium and calcium in a maritime forest in Chile, unaffected by atmospheric pollutants. In this study area they... 

For zinc surfaces, the rate of accumulation of substances is expected to affect the rate of corrosion of the metal. For aluminum in most environments, the passive surface oxide will protect the metal from further significant corrosion. Any interactions that occur on the surface will be among the accumulated substances and perhaps with the outermost layer of metal oxide. Interestingly, a few materials perform better in industrial atmospheres than in clean environments. Suzuki, et aL (17), have discussed the fact that weathering steel utilizes atmospheric pollutants, particularly sulfur dioxide gas, to form protective layers. 

Weather factors are of importance in site selection, site construction and site operation. Preliminary advice on the climatological picture will often point out potential atmospheric pollution hazards and help in making a decision on selecting one particular site out of several. 

R.U. Cooke, Crumbling heritage Studies of stone weathering in polluted atmospheres, National Power, Swindon, 1995. 

PVC may be attacked by aromatics, chlorinated organic compotmds, and lacquer solvents. PVC is resistant to all normal atmospheric pollutants including weather and UV degradation. 

With the exception of UV light stability, thermoset polymers resist weathering, being resistant to normal atmospheric pollutants. Refer to Table 3.3 for the atmospheric resistance of fiberglass reinforced thermoset polymers. 

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