Laboratory observation of dew formation at an early stage of atmospheric corrosion of metals

Dew formation process was conveniently observed using a specially devised e xperimental arrangement. A semiconductor cooling unit was adopted to chill the plate metal specimen, resulting in moisture condensation onto its surfa ce. Thus dewing process could be observed under metalloscope, and photograp hs of the dew droplets could be taken when necessary. Initially minute drop lets appeared upon the chilly surface. Then adjoining drops merged into a l arger one and thus dew drops grew gradually. Finally a thin water film cove red the whole surface of the specimen. In this way various influential fact ors could be evaluated with ease. When the specimen surface was covered wit h dust. dewing took place surrounding the dust with priority. On the salt p olluted surface dewing was much easier. This novel technique may provide an useful tool for study of early stage of atmospheric corrosion. (C) 2001 El sevier Science Ltd. All rights reserved.