Electrochemical behavior of Sn-xZn lead-free solders in aerated NaCl solution
Electrochemical corrosion behavior of Sn-xZn solder alloys (i.e. hypoeutectic Sn-6.5Zn, eutectic Sn-9Zn and hypereutectic Sn-12Zn, in wt.%) in aerated 0.5 M NaCl solution was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques, aiming to assess the effect of Zn content on the corrosion behavior of Sn-Zn alloys. Scanning electron microscopy (SEM) equipped with EDX, X-ray diffraction (XRD) were performed to characterize the surface morphology and to identify the chemical composition of the corrosion products, respectively. It is found that increasing Zn contents lead to an increase in corrosion current density and the corrosion potential shifted towards more negative values, revealing that the corrosion rates increase in the order of: Sn-6.5Zn <; Sn-9Zn <; Sn-12Zn. The acquired electrochemical impedances were successfully fitted with an equivalent circuit model. Fitted results reveal that total impedance decreased with increasing Zn content, indicating that Sn-6.5Zn alloy exhibits the highest corrosion resistance. The results are further confirmed by surface morphology characterization of the corrosion products, which shows a more homogeneous product film for lower Zn content. Analysis of the corrosion products indicates that oxide hydroxychlorides are the dominant corrosion products. Based on the obtained results, it is suggested that Sn-Zn alloy with lower Zn content appears to be more attractive in terms of superior corrosion resistance.
Electrochemical behavior of Zn-xSn high-temperature solder alloys in 0.5 M NaCl solution
Abstract Electrochemical behavior of Zn- x Sn ( x  = 40 wt%,30 wt%,20 wt%) high-temperature lead-free alloys was investigated in aerated 0.5 M NaCl solution by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. OCP results show that the corrosion state of the alloys working surface reached a relatively dynamic equilibrium after the alloys were immersed in 0.5 M NaCl solution for 100 h. EIS analysis reveals that the total corrosion resistance R t of alloys depended on the amount of Sn, and Zn-40Sn possessed the highest value 2228.2 Ω cm 2 . No passivation behavior was observed during corrosion process by potentiodynamic polarization measurement. The dominant corrosion products were confirmed as Zn 5 (OH) 8 Cl 2 ·H 2 O, ZnO and Zn(OH) 2 . Moreover, the surface and cross-section morphology of corrosion product suggested that the corrosion layer was more homogeneous and denser for higher Sn-content, Zn-40Sn obtained the best protective layer from corrosion product. The results recommend that Zn- x Sn high-temperature solder alloy with higher Sn content appears to be more attractive in terms of superior corrosion properties. The exact corrosion process was also discussed in detail.
The alcohol-aggression stereotype: a cross-cultural comparison of beliefs.
University students (N = 1,008) in eight countries participated in a survey aimed at mapping cross-cultural alcohol expectancies. Multisample structured means analysis was applied to compare changes in aggressive behaviors believed to occur in connection with drinking after "many" alcoholic drinks. Most subjects expressed the belief that intoxication was associated with greater aggressiveness, but there were significant national differences unrelated to self-reported alcoholic beverage preference, frequency of drinking to intoxication, or rates of personal involvement in episodes of alcohol-related aggression. Thus, the expectation that drinking leads to aggression may be determined to a significant extent by contextual factors and cultural traditions related to alcohol use.