Abstract
Acacia tortilis (AT) was extracted and characterized by gas chromatography-mass spectrometry (GC-MS). The eco-friendly corrosion inhibitor for aluminum matrix composites was investigated in 1.0 M HCl at 30-60 °C. The concentration of the inhibitor and time were varied in the range of 0 – 10 % v/v and 24-144 h. The inhibition studies were carried out using gravimetric method and potentiodynamic polarization. The surface morphology of the coupons was characterized by SEM/EDS techniques. The GC-MS revealed some elements/compounds (NCS, C-H, N or O). The inhibition efficiency increased with concentration and decreased with increase in temperature. The optimum inhibition efficiency of 89.60% was obtained at concentration of 8% v/v at 30 °C. Potentiodynamic polarization confirmed that the inhibitor acts as mixed types inhibitor. Activation energy (Ea) with inhibitor was higher than without inhibitor and proved to be physisorption. The thermodynamic parameters (standard free energy ΔG°), standard enthalpy (ΔHads) and standard entropy (ΔS) of the adsorption process were calculated. The inhibition mechanism of AT extract on Al-Si-Fe/15%SiC was physical and obeyed Langmuir adsorption isotherm. The protective layer on the composite surface confirmed the potential of the extract as corrosion inhibitor. The results of weight loss were in good agreement with those of electrochemical technique.
Highlights
Aluminum plays a key role in the development of metal matrix composites (MMCs) reinforced with a variety of ceramic materials including Al2O3, TiC, B4C, and SiC
Three coupons were withdrawn at the specific time, the surfaces were gently cleaned with iron brush to remove the corrosion products, weigh each coupon and take their average called weight loss
Gravimetric Method The gravimetric weight loss studies were carried out in 1.0M hydrochloric acid in the absence and presence of various concentrations of the plant extracts ranging from 2 to 10% v/v. The corrosion parameters such as corrosion rate, inhibition efficiency, surface coverage and the optimum concentration of the extract are presented in Table 2 and illustrated in Figures 1 and 2
Summary
Aluminum plays a key role in the development of metal matrix composites (MMCs) reinforced with a variety of ceramic materials including Al2O3, TiC, B4C, and SiC. Because of awareness of ecological risks, attention has been drawn to find more suitable inhibitors which are non-toxic and environmentally friendly inhibitors [11] Organic compounds containing both O, N and S atoms appear as better adsorption inhibitors because of their lone pair of electrons and polar nature of the molecules. That is why these compounds had been investigated by researchers [12,13,14,15,16,17]
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