Atmospheric corrosion local electrochemical response to a dynamic saline droplet on pure Iron

The electrochemical response to a dynamic 3.5% NaCl droplet on pure iron was investigated by newly developed concentric three-electrode array measurements. The freshly covered electrode surface of the volume-expanded droplet acts as the cathode in the corrosion cell, resulting in enhanced local anodic galvanic current density of the anode with steady area and position. As the thickness of a droplet with a constant covering area was reduced, the overall localized corrosion tendency declined, which can be attributed to a more homogeneous oxygen transfer process under a thinner droplet. The results suggest that dynamic droplets with increasing area coverage could promote and accelerate the initiation and propagation of atmospheric corrosion; whereas, the thinning droplets from its original geometry to a thin electrolyte film with an average thickness of 440 μm could decrease the tendency for localized corrosion. •New concentric three-electrode array electrochemical measurement was developed.•Local electrochemical response to dynamic changes in droplet geometry was characterized.•Droplets with an increasing area coverage promote atmospheric localized corrosion.