Relationship between corrosion rate of carbon steel and thickness of water film containing sea salt

Abstract

Atmospheric corrosion for carbon steel was discussed with taking notice of the relation of corrosion rate, CR, to the thickness of adsorbed water layer, d, onto deposited sea salt. Amount of water adsorbed by sea salt was weighed under various relative humidity, RH. Deduced concentration of the solution film was compared with that calculated thermodynamically, and the limitation for the application of thermodynamics was determined as a window of the amount of deposited sea salt, Ws, and RH. Within the limitation, d was evaluated from density of sea-salt solution and its concentration. Corrosion amount of carbon steel specimens exposed for a month under various Ws and RH was measured. Then, CR was obtained and d was calculated for each condition. The relation of CR to d showed a maximum CR = 0.07 mgm -2s-1 located adjacent to d = 50 μm.