Papers by Author: Jun Wang

Abstract: The microbiological influenced corrosion (MIC) behavior of the low alloy steel with granular-Zn-epoxy and flaky-Zn-epoxy coating in the sulfate-reducing bacteria (SRB) solution was investigated with electrochemical impedance spectroscopy (EIS), X-rays diffraction (XRD), scanning electron microscope (SEM) etc. Results show that the protection effect of the flaky-Zn coating specimen is much better than the granular-Zn coating one. The dissolution of zinc is more severe in granular-Zn coating than in flaky-Zn coating when the specimen immersed in the SRB solution. The shielding property of flaky zinc is much higher than granular zinc in the coating. The flaky-Zn coating is much more compact than the granular-Zn coating and therefore the property of anti-infiltration is much better. We may conclude that the flaky-Zn coating exhibited more favorable corrosion resistance property than the granular one.

Abstract: The MIC behavior of the ship plate steel specimen with LaCl₃-Zn epoxy coating in the sulfate-reducing bacteria (SRB) solution was investigated in this paper. The variation of corrosion potential over time of different specimens in SRB solution show that the corrosion potential of the specimen with LaCl₃-Zn epoxy coating was obviously higher than the Zn-epoxy coating, suggesting that the LaCl₃-Zn epoxy coating may offer better protection. The variations of lgflg |Z|=4.5 and f_h with time show that the property of anti-infiltration and corrosion resistance of LaCl₃-Zn coating is much better than the ones of Zn-epoxy coating. Results also show that more sulfides and corrosion products of LaCl₃-Zn epoxy coating were produced which increased the shielding property of the coating. The experimental results of XRD and SEM are in good agreement with the ones of E_corr, and EIS, etc. They all show that the LaCl₃-Zn epoxy coating exhibits more favorable corrosion resistance property than the Zn-epoxy coating. It is obvious that coating the ship plate steel with LaCl₃-Zn epoxy is an effective and promising method against the attack of SRB in marine environment.

Abstract: In the present study, the rare earths element YbCl₃ was added into the Zn-epoxy coating, and the MIC behavior of the low alloy steel specimen with YbCl₃-Zn-epoxy coating in the sulfate-reducing bacteria (SRB) solution was investigated and compared with the specimen of Zn-epoxy coating. Experimental results show that both the YbCl₃-Zn-epoxy and Zn-epoxy coating may offer effective protection for the basic low alloy steel. However, the corrosion potential of the specimen with YbCl₃-Zn epoxy coating was obviously higher than the Zn-epoxy coating, suggesting that the YbCl₃-Zn-epoxy coating may offer more favorable protection. Results of X-rays diffraction (XRD) and surface micrographs of specimens show that more sulfides and corrosion products of YbCl₃-Zn-epoxy coating were produced which increased the shielding property of the coating. The mechanism about the effect of YbCl₃-Zn-epoxy coating on MIC behavior was further discussed.

Abstract: The microbiological influenced corrosion (MIC) behavior of the low alloy steel with Zn-rich epoxy coating and micaceous iron oxide epoxy coating in the sterilized medium and sulfate-reducing bacteria (SRB) solution was investigated by using both full-coated and nicked-coated specimens. Results show that for steel coated with Zn-rich epoxy, the corrosion resistance of both full-coated and nicked-coated specimens was improved obviously. The Zn-rich epoxy coating protected the test steel effectively in the microbial environment with the cathodic protection in the earlier period and physical barrier protection in the later period. For steel coated with micaceous iron oxide epoxy coating, the corrosion resistance of full coated specimens was improved greatly. However, for nicked-coated specimens, corrosion was aggravated because the small anodic area around the nick accelerated the corrosion. It is concluded that the basic low alloy steel may be effectively protected by the micaceous iron oxide epoxy coating only when the steel is perfectly coated with the coating, breakage must be avoided.

Abstract: Effect of micaceous iron oxide epoxy coating on the microbiological influenced corrosion (MIC) behavior of the low alloy steel was studied. Samples uncoated or coated with micaceous iron oxide epoxy coating in sterile seawater and SRB solution was investigated by using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and so on. A series of data was obtained. Results show that micaceous iron oxide epoxy coating protected the base material effectively duo to its excellent physical barrier property.

Abstract: The microbiological influenced corrosion (MIC) behavior of the Cu-Ni alloy with or without Ni-P plating in the sterilized medium and sulfate-reducing bacteria (SRB) solution was investigated. Results show that severe pitting corrosion appeared on the uncoated specimens in both the sterilized medium and the SRB solution when the specimens coated with Ni-P plating were still in good condition. Since the Ni-P plating may offer both barrier and cathodic protection to the base metal. Besides, the structures of Ni-P plating and the passive film on the surface of the Ni-P plating are high uniform and amorphous without any structure defects. The non-crystalline structure may improve the corrosion resistance because it does not have crystalline defects such as dislocation, grain boundary, twin and so on which may cause corrosion easily. It is concluded that corrosion behavior of the Cu-Ni alloy with electroless Ni-P plating was improved greatly.

Abstract: The solute segregation to grain boundaries may be classified into equilibrium and non-equilibrium segregation. The models and kinetics calculation equations were proved in previous work. However, the computational task for grain-boundary segregation kinetics process is complex and cumbersome as it can involve a vast amount of numerical data. It is therefore necessary to develop an easily usable computational program which can provide the researchers with a powerful tool in grain-boundary segregation kinetics process analysis in addition to having a sound theory. A computational program of non-equilibrium grain-boundary segregation (NGS) kinetics of solute is therefore developed in this paper. It includes programs for critical time calculation, effective time calculation and diffusion coefficients calculation, the program of Auger Electron Spectroscopy test data disposal, the program of curve fitting and the program of NGS kinetics simulation. A simulation example by using the computation program of NGS kinetic equations is in good accordance with the experimental observation of phosphorus in steel 12Cr1MoV. The computational program of NGS is therefore proved to be appropriate and helpful.

Abstract: This paper studied structures of ceria-carbonate two-phase composites, with an emphasis on the interfacial structures and interactions between the two constituent phases of ceria and carbonate. The phase structure was analyzed by DSC, XRD and SEM. The IR measurements were carried out to identify the bonding situations and interfaces. Some new absorptions and wavenumber shifts of the bands appeared in IR spectra. There are strong indications of the interfacial phenomena exist in the two-phase composites through comparison between the two-phase composite with each individual constituent phases. The results opened a new interesting subject on the two-phase composite structures with significant importance for applications in advanced low temperature (300-600°C) SOFC.

Abstract: When failure occurs in material, it is often occurs by fracture along some grain boundaries and often by the micro-segregation of embrittling impurity to the grain boundaries. In the present work, the non-equilibrium grain-boundary segregation (NGS) kinetics of phosphorus and the temper embrittlement at the same solution treatment and different isothermal holding temperature in steel 2.25Cr1Mo are studied. The NGS kinetics curves of phosphorus at the same solution temperature （1050 oC ）and different isothermal holding temperature (540 oC and 600 oC) are given. Experimental results provide a direct evidence of NGS kinetic model and show that the grain boundary segregation concentrations of phosphorus for specimen isothermal holding at 540 oC are higher than those at 600 oC. The peak values of AES patterns of solute atoms for specimen isothermal holding at 540 oC are also higher than those at 600 oC. It is therefore concluded that the lower the isothermal holding temperature, the higher the segregation concentration of phosphorus at the grain-boundaries, and also the higher the degree of embrittlement.