Decheng Kong

Copper corrosion in hot and dry atmosphere environment in Turpan, China

Abstract The atmospheric corrosion behavior of pure copper exposed for three years in Turpan, China, which is a typical hot and dry atmosphere environment, was investigated using mass-loss tests, morphology observations, composition analyses, and electrochemical techniques. The results indicated that the annual corrosion rate of pure copper was approximately 2.90 μm/a. An uneven distribution of corrosion products was observed by scanning electron microscopy; this uneven distribution was attributed to the dehydration process during wet–dry and cold–hot cycles, and the compositions mainly consisted of cuprite (Cu 2 O) and atacamite (Cu 2 Cl(OH) 3 ). Electrochemical measurements showed that deposits on copper improved its resistance to corrosion and the protectiveness decreased with increasing temperature. On the other hand, results obtained using the scanning vibrating electrode technique showed that the porous and uneven structure of the deposit layer generated a spatial separation of cathodic and anodic reaction sites, which accelerated the corrosion process in wet and rainy weather.

Long-Term Corrosion of Copper in Hot and Dry Atmosphere in Turpan, China

AbstractnAtmospheric exposure tests were conducted on pure copper exposed to the atmosphere for a four-year period in Turpan, China, a typical hot and dry environment. The experiments included weight-loss tests, morphology observations, composition analyses, and electrochemical techniques. The results indicated that the annual corrosion rate of pure copper was approximately 2.24xa0g/m2/year, and an uneven distribution of corrosion products was observed by scanning electron microscopy. This was attributed to the dehydration process that occurred during wet-dry and cold-hot cycles. The corrosion products mainly comprised cuprite (Cu2O) and atacamite (Cu2Cl(OH)3). Electrochemical measurements showed that deposits on copper improved its resistance to corrosion, but the protectiveness decreased with increasing temperature.

Effect of Sulfide Concentration on Copper Corrosion in Anoxic Chloride-Containing Solutions

The structure and property of passive film on copper are strongly dependent on the sulfide concentration; based on this, a series of electrochemical methods were applied to investigate the effect of sulfide concentration on copper corrosion in anaerobic chloride-containing solutions. The cyclic voltammetry and x-ray photoelectron spectroscopy analysis demonstrated that the corrosion products formed on copper in anaerobic sulfide solutions comprise Cu2S and CuS. And the corrosion resistance of copper decreased with increasing sulfide concentration and faster sulfide addition, owing to the various structures of the passive films observed by the atomic force microscope and scanning electron microscope. A p-type semiconductor character was obtained under all experimental conditions, and the defect concentration, which had a magnitude of 1022–1023xa0cm−3, increased with increasing sulfide concentration, resulting in a higher rate of both film growth and dissolution.

Effect of chloride concentration on passive film properties on copper

ABSTRACT The semiconducting properties of passive films formed on copper, in anaerobic alkaline sodium chloride solution, were studied using Mott–Schottky analysis and electrochemical impedance spectroscopy, based on the point defect model. Results showed that the corrosion resistance increased with increasing potential, which was attributed to a well crystallised, refined grain structure, and a thicker passive film at higher potential. P-type semiconducting characteristics were obtained with or without chloride. The density of copper vacancies was approximately 1020u2005cm−3, and increased with the increasing chloride concentration, which was attributed to faster film-formation in a higher chloride environment. The diffusion coefficient of the defects, a key dynamic parameter for passive film breakdown, was in the range of 10−16–10−15u2005cm2u2005s−1, and increased with increasing chloride concentration, thus leading to a greater probability of pitting.

Effect of temperature on copper corrosion in high-level nuclear waste environment

Abstract The effect of temperature on the corrosion behavior of copper in simulated high-level nuclear waste environment was systematically studied. Electrochemical methods, including electrochemical impendence spectra, Mott–Schottky technology, cyclic polarization, and potentiostatic polarization, were employed to characterize the corrosion behavior of copper at different temperatures. Stereoscopic microscopy and scanning electron microscopy were used to examine the surface morphology, and X-ray photoelectron spectroscopy analysis was used to identify the composition of the passive film. The experimental results show that corrosion resistance of the passive film does not blindly decrease with the increase of temperature but increases at 60 °C owing to a compact outer layer; there is a potential for pitting corrosion, which decreases as the temperature increases. The main product of copper in an anaerobic aqueous sulfide solution is Cu2S but the content of CuS increases at higher temperatures. The whole passivation range shows p-type semiconductor characteristics and the magnitude of the acceptor density is 1023 cm−3, which increases with increasing temperature.

The stability of passive film growth on copper in anaerobic sulphide solutions

ABSTRACT The corrosion behaviour of oxygen-free copper in anoxic 0.1u2005M NaClu2009+u20092u2009×u200910−4u2005M Na2S·9H2O solution (pHu2009=u20099.0) was investigated under potentiostatic polarisation for different times. Electrochemical methods, including electrochemical impedance spectroscopy, Mott–Schottky analysis, localised electrochemical impedance spectroscopy (LEIS) and scanning electron microscopy observations, were conducted. The results indicated that the corrosion resistance of oxygen-free copper decreased with increasing applied potential, whereas it increased with increasing polarisation time. The passive film growth kinetics obeyed a logarithmic law (lnDu2009=u2009alntu2009+u2009b, where D is the layer thickness, b is a constant taken as the initial growth rate, t is the polarisation time and a is the time exponent). Subsequent to the formation of a compact and coherent passive film, the thicker the film was, the more difficult for ion to migrate, which further resulted in a slower film growth rate. The passive film displayed p-type semiconductor behaviour and the acceptor density (cation vacancy) was approximately 1022 to 1023u2005cm−3. The LEIS results showed that the passive film achieved relative stability after 24u2005h of immersion under natural conditions, which was longer than the duration of potentiostatic polarisation (4u2005h at −0.6u2005VSCE).

Corrosion Behavior of 316L Stainless Steel Fabricated by Selective Laser Melting Under Different Scanning Speeds

This work discussed the effects of different scanning speeds (800, 1083, 1200 and 1400xa0mm/s) on the microstructure of 316L stainless steel manufactured by selective laser melting (SLM) and the related corrosion behavior. Results showed that there were more voids with faster scanning speeds, and there were oxide powder and non-melt silicon inside the defects. The SLM 316L exhibited a full gamma austenite phase filled with sub-grains, and the average grain size of SLM-1083xa0mm/s 316L was approximately 42xa0μm, three times larger than that of the quenched 316L. The pitting potentials for the SLM 316L were all approximately 300xa0mV higher than that of the quenched due to the modification of inclusions in SLM, but the corrosion rate for the SLM 316L was faster, which was attributed to the voids and unstable passive film. The number of pitting sites increased with the scanning speed, and the pits occurred preferentially at the voids in SLM 316L.

Systematic Insight into Chloride Concentration, Applied Potential and Time Effect on the Passive Film of Cu-Zn-Ni Ternary Alloy in Alkaline Solution

The effects of chloride concentration, applied potential and time on the passive film of Cu-Zn-Ni ternary alloy in alkaline solution were systematically investigated using potentiodynamic and potentiostatic polarizations, electrochemical impedance spectroscopy, Mott–Schottky analysis, laser confocal microscopy, atomic force microscopy and x-ray photoelectron spectroscopy. Results showed that the pitting potential decreased as a linear function of log(

Surface monitoring for pitting evolution into uniform corrosion on Cu-Ni-Zn ternary alloy in alkaline chloride solution: ex-situ LCM and in-situ SECM

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