Inhibitor effects of sodium benzoate on corrosion resistance of Al6061-B₄C composites in NaCl and H₃BO₃solutions

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Sodium benzoate (SB) is used for the first time to inhibit the corrosion of Al6061-B 4 C composites in H 3 BO 3 and NaCl solutions. Al6061 100− x – x wt% B 4 C ( x = 0, 5, and 10) composites are manufactured by a powder metallurgy route. The corrosion inhibition efficiency of SB is investigated as a function of the volume fractions of B 4 C particles by using potentiodynamic polarization and electrochemical impedance techniques. Without the use of an inhibitor, an increase of the B 4 C particles in the composite decreases the corrosion resistance of Al6061-B 4 C composites. It is found that SB is an efficient corrosion inhibitor for Al6061-B 4 C composites in both investigated solutions. The corrosion inhibition efficiency of SB increases with an increase in B 4 C content. Since SB is an adsorption type inhibitor, it is envisaged that an extremely thin layer of molecules adsorbs onto the surface and suppresses the oxidation and reduction. It is found that the inhibitor effect of SB is more pronounced in a H 3 BO 3 environment than in NaCl solution. Further, the mechanism of corrosion inhibition by SB is illustrated by using optical and scanning electron microscopy of corroded samples. It is found that the adsorption of benzoate ions on the Al surface and its bonding with Al 3+ ions forms a hydrophobic layer on top of the exposed Al surface, which enhances the protection against dissolved boride ions.