Chengtao LI
金属学报(英文版)
The corrosion behaviors of alloy 690 in 1 wt pct sodium hydroxide aqueous solutions with and without PbO were characterized by electrochemical measurements, including potentiodynamic polarization, electrochemical impedance spectroscopy and Mott-Schottky measurement. The results reveal that there is a great difference between the corrosion behaviors of alloy 690 in the two tested solutions. The corrosion current density in PbO-containing solution is higher than that in the solution without PbO, which may be attributed to the anodic dissolution of metallic lead deposited at the early stage of polarization. The electrochemical impedance of the specimen in PbO-free solution is higher than that in the solution containing PbO. The slope of the Mott-Schottky curve in Pb-containing solution decreases notably compared with that in the Pb-free solution, which can be interpreted by the chromium depletion in the duplex structure of passive films.
关键词:
Alloy 690
,
电化学阻抗谱
,
氧化铅
,
Mott-Schottky曲线
,
钝化膜
F. Huang
材料科学技术（英文）
The oxidation behavior of alloy 690 exposed to high-temperature and high-pressure steam and water at 280 °C for 1 h was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). In high-temperature and high-pressure steam, the oxide film is composed of an outermost Ni-rich hydroxides layer, an intermediate layer of hydroxides and oxides enriched in Cr, an inner oxide layer. The film formed in high-temperature water is similar to that in steam, except for missing the Ni-rich hydroxides layer. Samples with different surface finishes (electropolished, mechanically polished, ground, and as-received) were prepared for comparison. A general increase of the oxide thickness with the degree of surface roughness is observed. The equivalent oxide thicknesses lie in the range of 100{200 nm for the as-received samples, 150{250 nm for the samples ground to 400# and 10−20 nm for the samples ground to 1500#, mechanically polished, and electropolished.
关键词:
Alloy 690
