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The problems associated with the corrosion of aluminum connections, the low mechanical properties of Al/Cu connections, and the introduction of EU directives have forced the potential of new materials to be investigated. Alloys based on eutectic Zn-Al are proposed, because they have a higher melting temperature (381 °C), good corrosion resistance, and high mechanical strength. The Zn-Al-Si cast alloys were characterized using differential scanning calorimetry (DSC) measurements, which were performed to determine the melting temperatures of the alloys. Thermal linear expansion and electrical resistivity measurements were performed at temperature ranges of −50 to 250 °C and 25 to 300 °C, respectively. The addition of Si to eutectic Zn-Al alloys not only limits the growth of phases at the interface of liquid solder and Cu substrate but also raises the mechanical properties of the solder. Spreading test on Cu substrate using eutectic Zn-Al alloys with 0.5, 1.0, 3.0, and 5.0 wt.% of Si was studied using the sessile drop method in the presence of QJ201 flux. Spreading tests were performed with contact times of 1, 8, 15, 30, and 60 min, and at temperatures of 475, 500, 525, and 550 °C. After cleaning the flux residue from solidified samples, the spreadability of Zn-Al-Si on Cu was determined. Selected, solidified solder/substrate couples were cross-sectioned, and the interfacial microstructures were studied using scanning electron microscopy and energy dispersive x-ray spectroscopy. The growth of the intermetallic phase layer was studied at the solder/substrate interface, and the activation energy of growth of CuZn, CuZn, and CuZn phases were determined. [ABSTRACT FROM AUTHOR]

Wetting of Al (99 %) pads by Sn-8.8Zn, Sn-8.7Zn-1.5In, and Sn-8.7Zn-1.5Ag (wt%) alloys was studied by means of the sessile drop method. The tests were carried out at 250 °C, using Amasan ALU33® flux, for up to 60 min. We used a setup that allows fast transfer of a sample to and from the hot zone of the furnace. Solidified alloy-substrate couples were cross sectioned and examined by scanning electron microscopy and energy dispersive X-ray analysis. The studied alloys wet Al pads as the wetting angles, determined after cleaning the flux residue from solidified alloy-substrate couples, are lower than 35 degrees. Wetting angles of Sn-8.7Zn-1.5Ag (wt%) alloy are higher and wetting areas are smaller than those of the remaining alloys, possibly due to a small gap between the melting and test temperatures. There is no clear dependence of the wetting angle and spreading area on time. Microstructures of cross-sectioned samples indicate that alloys dissolve the substrate and penetrate along grain boundaries. Since there is no significant difference between the same solder/Al interfaces at different wetting times, it is assumed that the microstructure evolves in <5 min. [ABSTRACT FROM AUTHOR]

Guar gum (GG) was investigated as a possible eco-friendly corrosion inhibitor for pure aluminium in a 1-M HCl solution at different temperatures and immersion times using gravimetric and electrochemical techniques. The results showed that GG was a good corrosion inhibitor for pure aluminium in the studied environment. The inhibition efficiency of GG increased with increasing inhibitor concentration and immersion time but decreased with increasing temperature. Polarisation measurements revealed that GG was a mixed type inhibitor with a higher influence on the cathodic reaction. The adsorption behaviour of the investigated inhibitor was found to obey the Temkin adsorption isotherm and the calculated values of the standard free adsorption energy indicate mixed-type adsorption, with the physical adsorption being more dominant. The associated activation energy (Ea) and the heat of adsorption (Qa) supported the physical adsorption nature of the inhibitor. Fourier-transform infrared spectroscopy (FTIR) and Raman/SERS were used to explain the adsorption interaction between the inhibitor with the surface of the metal. The results suggested that most inhibition action of GG is due to its adsorption of the metal surface via H-bond formation. [ABSTRACT FROM AUTHOR]