Abstract
Polarization resistance and potentiodynamic scan testing were performed on 316L stainless steel (SS) at room temperature in carbon nanotube (CNT)-water nanofluid. Different CNT loadings of 0.05, 0.1, 0.3 and 0.5 wt% were suspended in deionized water using gum arabic (GA) surfactant. Corrosion potential, Tafel constants, corrosion rates and pitting potential values indicated better corrosion performance in the presence of CNTs with respect to samples tested in GA-water solutions. According to Gibbs free energy of adsorption, CNTs were physically adsorbed into the surface of the metal, and this adsorption followed Langmuir adsorption isotherm type II. Samples tested in CNT nanofluid revealed a corrosion performance comparable to that of tap water and better than that for GA-water solutions. Among all samples tested in CNT nanofluids, the lowest corrosion rate was attained with 0.1 wt% CNT nanofluid, while the highest value was obtained with 0.5 wt% CNT nanofluid. At higher CNT concentrations, accumulated CNTs might form active anodic sites and increase the corrosion rate. SEM images for samples of higher CNT loadings were observed to have higher pit densities and diameters.
Highlights
Since the early discovery of nanofluids by Choi [1], these fluids have proven to possess unique properties due to the presence of particles that are of nanometer size (1–100 nm)
Covering part of the exposed surface with carbon nanotube (CNT) increased the resistance of charge movements, delayed the propagation of these pits and, decreased the corrosion rate, as can be seen from the smaller diameter of pits formed with nanofluids compared with those when tested in gum arabic (GA)-only solutions
The corrosion properties of the 316L stainless steel (SS) samples were tested under different types of solutions including CNT-water nanofluids, GA-water, deionized water, tap water and 3.5 wt% NaCl solutions
Summary
Since the early discovery of nanofluids by Choi [1], these fluids have proven to possess unique properties due to the presence of particles that are of nanometer size (1–100 nm). Nanofluid can be formed of different fluid bases such as water, ethylene glycol (EG), oils, and so on, and nanoparticles introduced to the base fluids can be metals [2,3,4,5], oxides [4,6,7,8], carbon nanotubes (CNTs) [9,10], among others This two-phase mixture has distinctive electrical, optical and thermal properties [11,12,13], which have allowed it to be used in many applications such as industrial heat transfer [14,15], transportation [16,17,18], biomedical [19,20] and solar applications [21,22,23]. These data were gathered to propose a mechanism for corrosion/inhibition of steel in presence of CNTs
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