Initial Corrosion Behavior of Carbon Steels under Airborne Sea Salt Deposition and Artificial Seawater Droplet

The initial corrosion behavior of carbon steels has been examined under airborne sea salt deposition and artificial seawater droplets in a chamber. The airborne sea salt was collected on graphite at a marine site for two hours. The droplets were prepared by dropping 5μl droplets of the artificial seawater using a micropipette. The diameter of the airborne sea salt particle was about 20μm at 30% R.H. (Relative Humidity), and it was about 1/10 compared with the artificial seawater droplets. As the relative humidity increases gradually, both the sea salt particles started to absorb the water from their environment. Both sea salts represented almost the same water absorption behavior as the thermodynamic calculation, but the artificial seawater droplets needed a longer time to transform into a liquid than the airborne sea salt. Furthermore, a corrosion test of carbon steels was conducted under the airborne sea salt deposition and the artificial seawater droplets, and the corrosion behaviors also showed different trends. The difference in the corrosion behavior is attributed to the water absorption behavior of the sea salt, that is, the particle size of the dried sea salt.