F.H. Cao
,
L. Guo
,
L.J. Zhang
,
Z. Zhang
,
J.Q. Zhang
金属学报(英文版)
The corrosion behavior of two different aged LY12 alloys in EXCO (234g/L NaCl, 50g/L KNO3, 0.1M HNO3) and MIL-H-600 (35g/L NaCl, 5g/L (NH4)2SO4) solutions were studied using electrochemical impedance spectroscopy (EIS) in conjunction with SEM technique respectively, and the pH variation of the above accelerated corrosion solution during materials corroding was also measured to characterize the corrosion processes. At the beginning of corrosion, EIS plots exhibited two capacitive arcs in the high frequency range (Cdl) and mediate frequency range (Clf) originating from the original corroded surface and the newly formed interface respectively, and a low frequency inductive loop due to the relaxation phenomenon of reaction intermediates. In the EXCO solution, the EIS results showed that once the exfoliation corrosion occurred, the inductive loop disappeared. The results also showed that the exfoliation corrosion susceptibility of state T6 is much higher than that of state T3, but the intergranular corrosion susceptibility has a reverse order. Based on the relationship of EIS results with SEM and metalloscopy morphologies of the corroding substrates and physic-chemical meaning of EIS parameters, an index (Clf / Cdl) has been proposed to characterize the extent of the localized corrosion, which variation tallies with the real corrosion extent correctly. Meanwhile, good agreement was found between the experimental results and the electrochemical model proposed and, good coherence between the electrochemical features and the distribution type of constituent particles of corroding material was observed.
关键词:
electrochemical impedance spectroscope
,
null
,
null
Z. Zhang
,
W.H. Leng
,
J.Q. Zhang
金属学报(英文版)
The influence of pH value of the electrolyte solution on the zinc electroplating process was studied by means of cyclic voltammetry and chronoamperometry approaches. The results shown that, under this experimental conditions and at high overpotentials, the nucleation of zinc is instantaneous, and the nuclear densities N increase with the overpotentials. While at low potentials, no distinguished nucleation current can be observed. High pH promotes the deposition either by drifting the initial depositing potential positively, or by increasing the depositing current through the change of the total charge of the adsorption process Qads, i.e., theｖstructure of electrochemical double layer.
关键词:
zinc electroplating
,
null
,
null
