The galvanic interactions between AA2024 and Carbon Fiber Reinforced Polymer under a dynamic drop of NaCl electrolyte were studied. The use of a dynamic electrolyte provided the unique opportunity to investigate both thick and ultra-thin electrolyte systems. A modeling approach was achieved by solving the Nernst-Planck equations in a 2D dynamic domain. Two kinds of boundary conditions were considered: electrochemical and physicochemical. Huge differences were found in the galvanic corrosion process at the beginning of the droplet evaporation (initial height 1.8 mm) and after 24 h of a continuum evaporation process at 25°C and 85% RH (final size 0.06 mm).
The gap between fully immersed and ultra-thin film electrochemical measurements is wide, which suggests that the two conditions are independent of one another. There is a lot of work describing experiments, results, and trends regarding completely immersed electrochemical tests. However, in corrosion tests under thin electrolyte films, the information is not so abundant. A classical three-electrode cell used in conventional electrochemical tests cannot easily be scaled for immersion in electrolytes of micron thickness. In fields such as atmospheric corrosion, for example, the thickness of the electrolyte could go from a few micrometers up to millimeters depending on the condensation-evaporation process.
The above justifies that modeling has recently become an essential tool for electrochemical predictions in such applications as several works have proved it.1-10 However, few works have been published to avoid oversimplification in models dealing with atmospheric corrosion problems that account for dynamic electrolytes under evaporation and condensation phenomena.3,6 The number decreases even more if the research also includes homogeneous chemical reactions and migration effects. Regarding the works of Montoya et al., they have been able to predict and validate the propagation of acidic and alkaline fronts by using both thick and thin chemically modified gel-electrolyte films during the galvanic corrosion phenomenon of different couples.8,9,11 However, it has always been achieved considering a static electrolyte.