研究大气腐蚀金属表面结露行为的新技术

A NOVEL LABORATORY TECHNIQUE FOR OBSERVING DEW FORMATION AT EARLY STAGE IN ATMOSPHERIC CORROSION

建立了一种在实验室直接观察金属表面结露过程的简便装置 .用半导体制冷器使片状金属样品快速降温 ,在金属表面上发生结露 ,同时用金相显微镜观察 ,还可照相记录 .该装置考察了尘埃、盐沾污等因素对于结露行为的影响 .

Although dewing is well recognized to play an important role in the atmospheric corrosion of metals, direct observation of dewing process has not been reported. In order to demonstrate the phenomenon in laboratory, a simple experimental arrangement was set up. Since dewing is a result of moisture condensation when metal surface is chilled down below the dew-point temperature of the air, a semiconductor cooling unit was adopted to cool the plate specimen. Thus dewing process could be observed under metalloscope, and photographs of the dew droplets could be taken when necessary. Initially minute droplets appeared upon cool surface. Then adjoining drops merged into a larger one and so drops grew gradually. Finally a thin water film covered entirely the specimen surface. In this way various influencing factors could be examined with ease. When the specimen surface was covered with dust, dewing took place surrounding the dust with priority. On the salt contaminated surface dewing was much easier. These illustrated unambiguously the enhanced effect of dust and salt contaminated on atmospheric corrosion.