Silver electrochemical migration results in the degradation of surface insulation resistance, and has been attributed to the dendritic bridge between adjacent conductors. In this paper, the electrochemical migration behavior of both Ag-plated Cu powder and pure silver powder in conductive thick film (CTF) are investigated. By Electrochemical migration test (water drop+ DC bias method), and the SEM and XRD examinations, it was found that the silver electrochemical migration in CTF was minimized when the Ag-plated Cu powder substitute silver powder in CTF. This is ascribed to the galvanic coupling effect that plays an important role in the migration inhibition. As sacrifice anode copper restrains the cathodic silver from dissolving in solution so as to decreases the probability of dendritic growth.
The effect of three organic additives in stannous methanesulfonate baths on cathodic overpotential and Faradaic impedance of tin-electrodeposition were studied by measuring cathodic polarization curves, galvanostatic responses and electrochemical impedance spectroscopy. The results show that the composite additive consisting of three organic compounds can significantly increase the cathodic polarization, crystallization overpotential and charge transfer resistance, which is very beneficial to improve coating quality and result in a fine-grained and smooth matt tin coating.
Zn-Ni alloy coatings were electrodeposited on low carbon steel substrate using a cyanide-free alkaline bath containing tetraethylenepentamine (TEPA) and triethanolamine (TEA) as complexing agents for Ni2+cations. Effect of TEA/Ni2+molar ratio on electrodeposition behavior, micromophology, Ni content and corrosion resistance of coatings were studied by means of SEM/EDS, polarization curve and electrochemical impedance spectroscopy (EIS), respectively. It was found that the deposition potential and elecctrochemical impedance of the cathode sample during the electrodeposition was influenced by the TEA/Ni2+molar ratio (TNmr) in the bath. The deposition potential shifts negatively and the impedance rises with increasing TNmrup to 2. The nickel content in Zn-Ni deposit was varied in a range from 16.81 to 19.04 wt.%. The dependence of cathodic current efficiency and depositing velocity of the coating on TNmrof plating bath were also determined. A fine-grained and smooth-faced coating was obtained at TNmr=2, which exhibited the highest corrosion resistance in 3.5% NaCl environment.
The corrosion behavior of a Cr15 super martensitic stainless steel (Cr15 SMSS) was investigated in NaCl solutions by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Effects of Cl-content, pH value and saturated CO2on corrosion were sdudied. It was found that the parameters of maintaining passivity current density (ip), the critical pitting potential (Eb) and charge transfer resistance (Rt) of Cr15 SMSS varied widely under different conditions. The corrosion resistance of Cr15 SMSS decrease with increasing Cl-concentration and lowering pH value. BothipandEbincrease for Cr15 SMSS in CO2-saturated NaCl solution, which verified that the CO2in NaCl solution can result in lower pitting sensitivity and higher uniform corrosion rate to Cr15 SMSS.
In this study, polyaniline are doped by composite acids (acetic acid/hydrochloric acid) in the process of chemical oxidation synthesis. The results of X-ray Diffraction show that the introduction of acetic acid improves the crystallization ability of polyaniline; Laser particle size analysis shows that with the increase of acetic acid in the proportion of composite acids, the average particle size of the product first decreases and then increases; FTIR shows that the main absorption peaks moved to lower frequency, which illustrate the effectiveness of doping by the composite acids; the introduction of ethanol in the system lead to a lower doping level.
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