Enhanced Passivation of Aluminum via Cooperative Effects of Silica Nanoparticles and SDBS in Chloride Environments

Abstract

Abstract. The need for efficient thermal-management options has gained acute importance in contemporary energy systems and for a wide swath of current engineering applications, ranging from automotive cooling and industrial heat exchangers to concentrated solar power and next-generation thermal desalination technologies. As the demand for higher thermal performance gains exigence, exploration of novel heat-transfer fluids (HTF) is gaining popularity for simultaneously improving both thermal efficacies as well as additional functional benefits (including protection from fouling and corrosion resistance). Solvents doped with minute concentrations of nanoparticles (i.e., nanofluids) can be an attractive option in these endeavors. Although these nanofluid formulations show promise, their direct interaction with metal components raises important questions about the material compatibility issues. The focus of this study, therefore, was to explore the benefits of various types of additives in neat HTF samples, such as when mixed with silica nanoparticles [silicon dioxide (SiO2)] only, as well as for silica nanoparticles mixed with a surfactant (in these solvents), such as sodium dodecyl benzene sulfonate (SDBS). The influence of these additives and formulations on the resulting corrosion resistance was explored in this study. The scope of this study was confined to aluminum substrates (that were exposed to chloride ions). The neat solvent deployed in these experiments was chosen as a 0.01 M sodium chloride solution. The neat solvent was then doped with silica nanoparticles at a concentration of (a) 0.05% and (b) 0.1% by mass. Subsequently, additional types of silica nanofluid samples were synthesized by mixing with SDBS, i.e., (c) 0.05% silica + 0.05% SDBS and (d) 0.1% silica + 0.1% SDBS (by mass), respectively. Electrochemical tests were performed for each of these test fluids (neat solvent sample and nanofluid samples) to ascertain their effectiveness in enhancing the corrosion resistance of freshly prepared aluminum substrates. Corrosion resistance was quantified using these electrochemical tests consisting of measurements of: (i) open-circuit potential, (ii) linear sweep voltammetry, and (iii) cyclic voltammetry. The experimental results showed distinct differences in how additives, such as nanoparticles (e.g., silica) and surfactants (e.g., SDBS), can affect the unique surface characteristics and material compatibility puissance of freshly prepared aluminum substrates (when exposed to corrosive medium), thus highlighting their vigor as potential additives for synthesizing novel HTF samples, such as for immersion cooling (e.g., for electronics chip cooling), transportation (e.g., for automotive), and desalination applications (where enhancing the efficacies for both thermal management and their corrosion resistance is critical).