Sunshine hours

TOW depends mainly on the meteorological parameters, the nature of the metal, the properties of the metallic surface and of the corrosion products layer formed. The most important climatic factors on the corrosion process are relative humidity, sunshine hours, temperature of the air and the metal surface, wind velocity and duration and frequency of the rain, dew and fog. 

Total Horizontal Solar Insolation and Sunshine Hours for Some Developing Countries... 

With very few exceptions, the developing countries are situated in climatic zones of the world where the insolation is considerably higher than the world average of 3.82 kWh/m day [153]. In Table 14.1 daily average horizontal insolation data and sunshine hours are given for some developing countries [152,154],... 

Direct sunlight stability studies normally involve exposures in the UK and, for example, at Curasao (off the northern coast of Venezuela), and sometimes also at Phoenix, Arizona, which has much drier climatic conditions than Curasao. The number of sunshine hours per day in tropical areas is at least double that in the UK and the light is of higher intensity. Once reliable basic data have been established, it is possible from the results obtained from exposures in tropical areas to predict the outdoor life of plastic formulations in temperate climates with reasonable accuracy. 

Outdoor life (sunshine hours) Outdoor life (sunshine hours) ... 

Colours + 0.5% UV stabiliser Outdoor life (sunshine hours) Screening power relative to natural non-UV stabilised polymer Screening power relative to non-UV stabilised pigment formulation... 

Excellent protection is afforded by a range of carbon blacks for the weatherability of PP. Although the average particle size of the carbon blacks tested, as measured by electron microscopy, varied from 16 to 38 pm, at a concentration of 2%, none of the PP showed a significant fall-off in MW after 6,000 sunshine hours exposed under tropical conditions at Curasao. For the small-particle-size carbon black, a reduction in concentration to 0.5% gave similar results (see Figure 18.57). 

Researched colour Sample thickness (mm) Number of failures Time to rupture (sunshine hours) Time to onset of crazing (sunshine hours) Outdoor life in non-stressed state (sunshine hours)... 

Curasao Non-UV stabilised to direct sunlight No crazing, but distinct surface powdering after 2,400 sunshine hours exposure Slight loss of gloss observed after 800 sunshine hours exposure... 

Excellent protection is afforded by a range of carbon blacks on the weatherability of polypropylene. At a concentration of 2% of a carbon black in the 15-40 pm particle size range, polypropylene did not show a significant fall-off in molecular weight after 6000 sunshine hours exposure in a tropical climate. This would be almost 12,000 hours in temperate climates. 

Country Average Insolation (kWh/m tlay) Sunshine Hours (h/d)... 

Access to new and more sensitive analytical techniques has resulted in substantial progress in the characterization of corrosion products formed under both laboratory and field exposure conditions. These techniques permit the determination of, e.g., thickness, chemical composition, and atomic structure of corrosion products formed at both early and later stages of exposure. When combined with environmental data, such as deposition rates of corrosion-stimulating atmospheric constituents, relative humidity, temperature, and sunshine hours, the new techniques have resulted in a more comprehensive understanding of the complex processes that govern atmospheric corrosion. In a series of papers, Graedel has summarized the corrosion mechanisms of zinc [62], aluminum [63], copper [18], iron and low-alloy steel [64], and silver [19]. It is beyond the scope of this chapter to provide... 

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