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Salt‐induced iron corrosion under evaporating sessile droplets of aqueous sodium chloride solutions
Author(s) -
Soulié V.,
Lequien F.,
FerreiraGomes F.,
Moine G.,
Feron D.,
Prene P.,
Moehwald H.,
Zemb T.,
Riegler H.
Publication year - 2017
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201609319
Subject(s) - aqueous solution , chloride , corrosion , electrolyte , cathodic protection , evaporation , sodium , salt (chemistry) , metal , anode , chemistry , materials science , sodium sulfate , inorganic chemistry , chemical engineering , metallurgy , electrode , thermodynamics , physics , engineering
The corrosion process induced by evaporation of sessile droplets from aqueous sodium chloride solutions on planar iron surfaces was quantitatively investigated. The spatial distribution of the salt inside the evaporating sessile droplet, which is influenced by the initial salt concentration in the droplet bulk, is correlated to the localization of the anodic and cathodic reactions at the electrolyte–metal interface over the footprint droplet area. At low salt concentration, the inverse of the classical well‐accepted Evans model is observed due to the hydrodynamic flows linked to evaporation: the anode area is established near the three‐phase contact line region. Increasing salt concentration leads to a more uniform pitted sessile droplet: we observed locally anodic and cathodic areas over the droplet surface at the metal–electrolyte interface, where local variations in chloride concentrations occur. In addition, the presence of corrosion products and some pits demonstrate that pitting corrosion takes place if the salt concentration reaches a threshold value, experimentally determined by an optical set‐up.