Effect of Al2O3 nanoparticles on the corrosion behavior of aluminum alloy in simulated vehicle coolant

Abstract

The use of nanofluids as vehicle coolant can significantly improve the heat exchange efficiency, but it is necessary to understand its corrosiveness to metals before use. Corrosion behavior of aluminum alloy in simulated vehicle coolant (SVC), nano Al2O3 coolant (SVC-Al2O3), simulated coolant containing sodium dodecyl benzene sulfonate (SVC-SDBS) and nano Al2O3 coolant containing SDBS (SVC-Al2O3-SDBS) was investigated by electrochemical impedance spectroscopy, polarization curve, weight loss analysis and surface analysis in this paper. The results showed that in the three media of SVC, SVC-SDBS and SVC-Al2O3-SDBS, the impedance modulus at the frequency of 10 mHz |Z|0.01, the charge transfer resistance Rct and the film resistance Rf of aluminum alloy electrode increased with the immersion time. Compared with the three media, the aluminum alloy in SVC-Al2O3 medium had the lowest |Z|0.01, Rct and Rf, and had the highest corrosion current density, implying that Al2O3 nanoparticles promoted the corrosion of aluminum alloy in SVC, and the corrosion products formed on the alloy surface were Al2O3, Al(OH)3, AlOOH, which were loose and not protective. The Rf values of aluminum alloy electrode increased significantly with time in the media containing SDBS. The aluminum alloy exhibited the best corrosion resistance in the medium of SVC-SDBS and no obvious loose corrosion products but compact passivation film could be seen on the alloy surface. SDBS exhibited a good corrosion inhibition effect on aluminum alloy, which may be due to the adsorption of SDBS on the metal surface and the fact that SDBS promoted the formation of the passive film by preventing the transformation of alumina film to loose AlOOH layer. In the medium containing both SDBS and Al2O3 nanoparticles, the corrosion inhibition effect of SDBS was weakened. This maybe due to the electrostatic attraction of positively charged Al2O3 nanoparticles and negatively charged SDBS, which reduced the adsorption of SDBS on the metal surface, thereby weakening the protective effect of SDBS on the metal surface.