Micro-droplets phenomenon and atmospheric corrosion - I. Formation and spreading of micro-droplets

The formation of the electrolyte droplet due to the deliquescence of soluble salt particles is one of the cause for the acceleration of atmospheric corrosion. A lot of micro - droplets, 1 μm-10 μm in diameter, were observed around the edge of the main - droplet formed by the deliquescence of salt particles deposited on metal surface in atmosphere. In this paper, the characteristics of the formation and spreading of the micro - droplets were investigated in detail in a humidity - controlled chamber. The results showed that oxygen, relative humidity and a combination of salt particles and metals played important role in the formation of micro - droplets. Two premises were necessary for the formation of micro - droplets in atmosphere. First, the relative humidity should exceed the saturated relative humidity of the main - droplet. Another was that the metal substrate could be eroded under the main - droplet.