Anodic Electrochemical Performance and Microstructure of Novel Aluminum Alloys

1 Introduction Aluminum has a negative standard electrode potential, a large electrochemical equivalent, and abundant natural resources. Its aluminum air (AH)2) half-fuel cell or aluminum-silver oxide (Al-AgO) seawater battery not only has long service life and high ratio. Energy, high specific capacity, but also has the advantages of no environmental pollution, no noise, low cost, etc. For decades, this research has been highly valued by the energy, transportation, telecommunications, defense and other departments of many developed countries, many scientists are committed to Research and development of high-performance aluminum alloy anodes, while applying research on A-O2 batteries for automobiles and A-AgO batteries for underwater thrusters, and corresponding battery design 2001—this paper studies the anodes of new aluminum alloys. The electrochemical performance and self-corrosion rate of the material in 25% KOH+3.5% NaCl medium and the microstructure of the aluminum alloy affect the performance.

2 Test methods Plasma spectrometers were used to determine the micro-compositions of materials. According to alloy Ga-Mg) alloy. Weigh 99.99% pure aluminum and the required amount of various alloying elements and smelt with graphite crucible in an electric resistance furnace. After the aluminum is completely melted in the crucible, the previously weighed alloy chemical elements are added to the aluminum melt in sequence. After mixing with a graphite rod, the alloy melt is poured into a water-cooled steel mold, and the ingot is subjected to annealing after milling, hot rolling, cold rolling, and finishing rolling into a 1.0 mm thick aluminum alloy sheet.

2.1 Electrochemical Performance Test The above pure aluminum and aluminum alloy plates were respectively made into an area of ​​1.0cm2 of the electrode to be tested (the surface of the electrode was not polished), numbered as No. 1, No. 2, and No. 3, respectively. The platinum electrode was used as an auxiliary electrode. A 6.0 cm2 mercury/HgO electrode was used as a reference electrode. The electrolyte chemistry tester was used to determine the electrochemical performance of constant current and potentiodynamic polarization.

2.2 Observation of microstructure and surface morphology The microstructure of the aluminum alloy was observed with a metallographic microscope after the sample was mounted by mounting, coarse grinding, mechanical polishing, and electrochemical polishing. The KYKY-2000 was used as the sample after the electrochemical performance test. Scanning electron microscope observation of the surface morphology after etching 3 Results and discussion 3.1 Impurity analysis of samples The impurity content of pure aluminum and its alloys are shown in Table 1. Table 1 Sample Impurity Content Mass fraction/wt Specimen number 3.2 Microstructure and corrosion The apparent metallographic microstructure of 99.99% Al and the new aluminum alloy is shown in Fig. 1. It is known that pure aluminum forms a large second phase compound due to impurities or aluminum, resulting in many etch pits on the surface of aluminum (middle black portion. ) The surface erosion is extremely uneven and the surface film is denser. As can be seen, the developed new multi-element aluminum alloys No. 2 and No. 3 have uniform aluminum matrix structure, a part of the added alloying elements is solid-dissolved in the aluminum matrix crystal lattice, and part of the alloy elements are evenly dispersed in the grain boundary; The surface erosion of No. 2 and No. 3 specimens was uniform, and the surface film was loose and porous.

3.3 Corrosion rate The corrosion rate of a new type of aluminum alloy with 99.99% pure aluminum in a 25% cracker + 3.5% Shi 0 medium is shown in Table 2. Table 2 shows that the self-corrosion rate of pure aluminum is relatively large, and the new table 299.99% Al and The corrosion rate of the alloy electrode open circuit potential / mV material (vsHHgO) corrosion rate electrode potential / mV No. 1 on the 2nd No. 3 aluminum alloy corrosion rate is greatly reduced. When the aluminum electrode is corroded in the medium, the cathodic hydrogen evolution process takes place preferentially on the cathode phase or inclusions with low hydrogen overpotential, and the most common traces of the poorly electrochemically active Si (―0.445 V), Fe(―) are present in pure aluminum. Impurities such as 0.447V), Cu (―0.340V), or micro-cathodes that are poorly electrochemically active with aluminum–6. These impurities have electrochemical and physical inhomogeneities. When contacted with an electrolyte, they are micro- Corrosion microcells in which the cathode phase forms a short circuit with the anode of the aluminum substrate, the hydrogen depolarization corrosion is accelerated, ie, the corrosion of the substrate metal aluminum is accelerated and the corrosion is extremely uneven (see). Therefore, the corrosion rate of pure aluminum in alkaline sodium chloride medium The large-scale aluminum alloys No. 2 and No. 3 developed in Table 1 have increased the hydrogen evolution overpotential of the cathodic phase reaction due to the addition of high hydrogen overpotential elements Ga, Pb, etc., ie, in the micro-cell system. The cathodic depolarization is weakened, and the precipitation of hydrogen gas in the cathode phase on the surface of the aluminum alloy electrode is retarded, thereby preventing the dissolution of the aluminum in the matrix metal, that is, reducing the corrosion rate of the anode in the alkaline sodium chloride solution. In the alloy elements added to the high activity such as magnesium, aluminum cathode micro impurities such as Si phase in the electrochemically active aluminum is converted into (a 0.85V) similar compound Taicy, Gary.LSPat Masu Qing. Underwater propulsion with high-energy batteries. Shipboard Technology, 1999 (1).

Li Zhenya. Aluminum-water battery research. Power Technology, 1997, 21(1): Zhang Chengzhong. Metal corrosion and protection. Beijing: Metallurgical Industry Press, 1985. Wei Baoming. Metal corrosion theory and application. Beijing: Chemical Industry Press, 1984. Liu Gonglang Aluminium Alloy Smelting Foundry Technology. Chinese rot Zhao Yuehong. Influence of Microstructure Inhomogeneity of Aluminum Alloy Sacrificial Anode on Its Corrosion Rare metal, 2 (1) 0 Qigongtai. Study on the Relationship between Microstructure and Electrochemical Properties of Aluminum Alloy Sacrificial Anodes . corrosion