Synergistic inhibition of zinc corrosion in 0.5 M NaCl by combination of cerium(III) chloride and sodium silicate

The synergistic inhibition effects of cerium(III) chloride, CeCl3 and sodium silicate, Na2Si2O5 (water glass) on corrosion of zinc in an aerated 0.5 M NaCl solution at 30degreesC were examined by polarization measurements. Equimolar mixtures of these inhibitors were markedly effective, indicating that the inhibition efficiencies of the mixture at 1 x 10(-4) of each inhibitor were 95.9 and 93.6 after immersion of a zinc electrode in the solution for 3 and 120 h, respectively. X-ray photoelectron spectra revealed that a protective layer composed of hydroxylated or hydrated cerium-rich oxide and small amounts of zinc hydroxide and silicate formed on the zinc surface. A high inhibition efficiency of 1 x 10(-3) M Na2Si2O5, 97.7% was obtained for corrosion of a zinc electrode which was previously treated in the NaCl solution of 1 x 10(-3) M CeCl3 at 30degreesC for 30 min. (C) 2002 Elsevier Science Ltd. All rights reserved.