Corrosion of Copper Alloys in Consumer Electronics Environments
C Results of corrosion testing on eight alloys from five copper alloy families common in the consumer electronics industry—copper nickel tin (CuNiSn), copper beryllium (CuBe), copper titanium (CuTi), phosphor bronze (CuSnP), and Corson alloys (CuNiSiX)—are presented. Short-term exposures were conducted in simulated consumer environments such as a salted carbonated cola beverage, artificial human perspiration, and phosphate-buffered saline. Longer-term, conventional salt fog testing, up to 1,000 h, was also conducted. In all of these tests, CuNiSn showed the lowest corrosion rate followed closely by CuBe alloys. Corrosion rates of CuTi alloys were consistently the highest after shortterm testing, while CuSnP showed the highest corrosion rate after salt fog testing.
Corrosion Behaviors of Supersaturated and Peak-Aged CuNiSiCr Alloys under Salt Spray Environment
As promising substitutes for Cu-Be alloys, Cu-Ni-Si series alloys have been investigated intensively concerning their mechanical and electrical properties but without much attention on their corrosion performance. Herein corrosion behaviors and mechanisms of the supersaturated and peak-aged CuNiSiCr alloys are investigated using salt spray test, x-ray diffraction, scanning and transmission electron microscopes. The corrosion rate of the aged sample is lower than that of the supersaturated one due to forming a denser protective corrosion product, Cu2O. Theoretical analyses indicate that the Cu2O film grows by oxidization of the matrix and its granular size is greatly influenced by the precipitates. The second corrosion product Cu2(OH)3Cl/CuCl2·3Cu(OH)2 forms by consuming the oxide Cu2O, which will induce pitting and deteriorate the corrosion resistance. Based on the obtained results, guidance concerning the composition and treatment optimization is provided for enhancing the anti-corrosion capability of the CuNiSiCr alloys.
Comparative study of in vitro flow characteristics between a human aortic valve and a designed aortic valve and six corresponding types of prosthetic heart valves.
A model of a pulsatile cardiovascular system is described including an electronic control, a hydraulic driving unit, a volume storage, a peripheral resistance and measuring equipment. Six different artificial heart valves, a designed aortic valve (Aachen pockett valve II) and a human aortic valve have been tested in the outflow position of the pump. Three of them are presently being used in clinical applications. Measurements of pressure and volume flow have been obtained for different frequencies n, pump volumes Vp and time ratios between pressure and suction phase. From the experimental results a comparative evaluation was deducted for different working conditions. In comparison to natural human aortic valve (NK) large volume flow is verified by the Aachen pocket valve II (AT), the Gott-Dagget value (GD), the Starr-Edwards valve (SE) and the Lillehei-Kaster valve (LK). The Gott-Daggett valve has the smallest back flow volume. The Smeloff-Cutter and in particular the Wada-Cutter valve have the largest regurgitation. This is to be expected since the Cutter valves are purposely so designed that they do not close tightly in order to avoid blood sedimentation. The human aortic valve, the Gott-Daggett valve and the Aachen pocket valve demonstrate the most favourable opening-closing characteristics. The human aortic valve achieves a negligible pressure loss, followed by the Björk-Shiley and the Lillehei-Kaster valve.