Corrosion behavior of alloys for hot dipping

The corrosion property of three currently used hot dipped alloys (Al-8Si, Zn-0.6Ni and 55Al-Zn-Si) immersed in 3.5% NaCl solution were studied by analyzing the open circuit potential variation with time and electrochemical impedance spectroscopy (EIS) tests. The open circuit potential of the Al-8Si alloy is 100mV higher than the potential of Zn-0.6Ni and 55Al-Zn-Si, and the potential of Zn-0.6Ni is approach to the 55Al-Zn-Si alloy. The phase angles of the Al-8Si, 55Al-Zn-Si and Zn-0.6Ni are close to -80 degrees,-70 degrees,-60 degrees, and the high impedance values at low frequencies are 10(5),10(4),10(3) Omega cm(2), respectively. The EIS spectra of the alloys indicated two relaxation time constants. An "equivalent circuit" with the circuit elements representing the electrochemical properties was proposed to simulate the EIS spectra, and the simulated dates were in a good agreement with the experiment dates. The polarization resistance (R-p) of Al-8Si, 55Al-Zn-Si and Zn-0.6Ni are 18000, 2010, 251 Omega.cm(-2), respectively. The results showed that the corrosion property of Al-8Si is well than the other alloys in the test solution.