Protezioni ottiche in Teflon® per sensori di radiazione solare in acqua marina

An applicative limit in the use of optical sensors, in underwater surveys, is due to the colonization, of transparent or translucent parts of the devices, by micro organisms, plants, algae and / or animal (bio-fouling). Several methods were proposed to reduce this problem and thus to increase the time interval between a maintenance and a next one, of the transparent or translucent parts, of the devices. When the underwater optical devices are gauges of intensity of global radiation or in wide spectral radiation bands, it doesn't need that the protection system maintains a perfect transparency, but it is sufficient that is adequately translucent. This paper takes into account the instruments (radiometers) for the qualiquantitative measures of solar radiation which can penetrate, to different depths, in sea water. In particular it refers to the global radiation, and these bands of the radiation that are necessary to the life of underwater vegetation. Many studies have shown that the glass, in sea water, is rapidly colonized but it becomes biorepellent if it is treated in surface with oxides such as: titatium oxide (TiO2) or tin oxide (SnO2). In this work we set out to verify whether this treatment could also improve the performance of Teflon® optical protections mounted on many underwater radiometers. To this end certain Teflon® protections, untreated, were compared to Teflon® protections, treated with SnO2, to glass protections, treated with SnO2, and to glass protections, treated with TiO2 and SnO2. The tests, conducted at sea, showed that the Teflon® keeps the value of transmittance practically constant over time, for a longer period than glass from three to ten times. But the most interesting result was that the transmittance of the Teflon® over time is constant regardless of whether it is treated or not. In other words, for Teflon®, the surface treatment with SnO2 seems to have no effect on bio-fouling.