Cerium(III) chloride and sodium octylthiopropionate as an effective inhibitor mixture for zinc corrosion in 0.5 M NaCl

Abstract

It has been reported that cerium(III) chloride CeCl 3 and sodium octylthiopropionate C 8H 17S(CH 2) 2COONa (NaOTP) are effective inhibitors for zinc corrosion in 0.5 M NaCl. In this study, synergistic inhibition of zinc corrosion in an aerated 0.5 M NaCl solution by a mixture of these inhibitors was investigated by polarization measurements after immersion of a zinc electrode in the solution for many hours. The inhibition efficiency of 1×10 −4 M CeCl 3 plus 1×10 −5 M NaOTP mixture was high, 95.1% after both 3 and 120 h. X-ray photoelectron spectroscopy and electron-probe microanalysis for the inhibited electrode revealed that the zinc surface was covered with a protective film composed of an hydrated or hydroxylated Ce-rich oxide, a small amount of Zn(OH) 2 and a trace of Zn(OTP) 2 chelate. The inhibition effect of 1×10 −5 M NaOTP in the NaCl solution for the zinc electrode previously treated in 1×10 −3 M CeCl 3 for 30 min was also examined, indicating a higher inhibition efficiency, 96.3% after immersion of the electrode in the solution for 120 h.