Salt‐induced iron corrosion under evaporating sessile droplets of aqueous sodium chloride solutions

Abstract

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.

Uniform, Anticorrosive, and Antiabrasive Coatings on Metallic Surfaces for Cation–Metal and Cation−π Interactions

“…Even after a week, this significant difference remained (Figure S4). Notably, it is well-known that cations generally accelerate the corrosion of metals due to an electrochemical reaction. − In our experiments with the bridging complexing agent EDA, however, we successfully suppressed the coffee-ring effect using complexed cations and avoided the electrochemical reaction to reduce the corrosion rate. In this process, the EDA molecules firstly complexed with Zn 2+ to dissolve Zn 3 (PO 4 ) 2 in solution and then were gradually evaporated with water to form a uniform PS microsphere coating with insoluble Zn 3 (PO 4 ) 2 to avoid electrochemical corrosion.…”

“…Inspired by this, cations themselves might be in actual the best anticorrosive protectors because they have been oxidized. Unfortunately, it is well-known that conventionally cations greatly accelerate the electrochemical reaction leading to the electrochemical corrosion of metal surfaces, − hindering their applications in coatings. In this electrochemical corrosion, the cations acting as the electron carriers in the solution or water films on the metallic surfaces greatly accelerate the electron transformation to increase its electrochemical corrosion reaction.…”

Influence of Cations on Direct CO2 Capture and Mineral Film Formation: The Role of KCl and MgCl2 at the Air/Electrolyte/Iron Interface

“…In the first part of the mechanism, corrosion is needed to produce active sites before mineral films can be grown on iron surfaces, as shown from the PM-IRRAS results and the AFM measurements. In steps (1−2) surface corrosion is initiated by the chloride anions through pitting of the native oxide layer on the iron surface, 53 thus creating defects that act as nucleation sites for the film growth, 65 according to the surface roughness measurements. This then allows for (2) reduction−oxidation to occur followed by hydroxylation of the surface.…”

Development of a novel method for the in-situ dechlorination of immovable iron elements: optimization of Cl− extraction yield through experimental design

“…As major component of marine aerosols, Cl − ions trigger physical and chemical weathering of Built Heritage materials 4 – 6 . Focusing on iron-based components (both structural and ornamental), chlorides infiltration promotes the formation of unstable corrosion phases that accelerate deterioration processes 7 – 11 . Among them akaganeite (FeO 0.883 (OH) 1.167 Cl 0.167 ), which chemical structure is characterized by tunnels (filled by chloride ions) parallel to the c-axis of the tetragonal lattice, tends to form low density rust layers 12 , whose high fragility facilitates cracking and exfoliation phenomena 13 , 14 .…”