- 學位論文
黃銅之腐蝕與電解溶出及鈍化
Corrosion, Electrolytic Dissolution and Passivation of Brass
摘要
本研究以報廢彈藥中的黃銅金屬為研究對象，主要目的為提出一對環境較友善且能將報廢彈藥有效處理之方法，並將彈藥中可用之資源(如銅、鉛)加以回收，以電化學方法研究其中反應之原理。首先嘗試以硫酸侵蝕黃銅，使用線性極化電阻法(LPR，Linear Polarization Resistance)，改變硫酸濃度、樣品表面清潔程度及溶液中氯離子濃度等條件，測定.22 LR、9 mm、.38 SPL及.45AUTO等彈藥中之黃銅在不同條件下之腐蝕速率，最終測得最快之腐蝕速率為14.45 mpy，經換算後得知至少需1.24年才能將該彈藥外殼完全溶解，除時間成本過長外，僅依靠腐蝕速率進行推估並無法保證實際處理效果。為減少處理時間，導入法拉第電解定律，使黃銅電解溶於電解液中，改變通過電流、硫酸濃度及氯離子濃度等操作參數，實驗結果指出實際主導電解反應速率之參數為操作電流。然而在樣品表面上之電流密度過高時，可能使得金屬表面生成金屬氧化物附著，出現陽極鈍化現象干擾電解反應。陽極鈍化為常用的防腐蝕技術，但對於本研究之電解處理方法具有負面影響，於是使用計時電位法(CP，Chronopotentiometry)，測試90分鐘內，200 mA/cm2的高電流密度下，0.25M、0.5M、1M硫酸靜止與攪拌溶液中，黃銅的鈍化情形，實驗後發現加入磁石攪拌電解液幾乎可避免黃銅電解時陽極鈍化發生，且於1M的靜止硫酸液中，樣品黃銅的鈍化情形最為嚴重，故以次條件進行加入氯離子之實驗，加入0 ppm、30 ppm、60 ppm、90 ppm氯離子之鈍化時間分別5.4、4.2、6.3、9.0分鐘，可小幅延遲鈍化發生的時間。
並列摘要
Brass metal exists in waste ammunitions is the target of this study. The main purpose is to propose a environmentally friendly and effective process for scrapping waste ammunitions, recycling the available resources (copper and lead) from these ammunitions, and studying principles of the reactions with electrochemical process. First, try to corrode brass with sulfuric acid. Use linear polarization resistance (LPR) method to determine the corrosion rate of brass from four models of ammunition (.22 LR, 9 mm, .38 SPL and .45AUTO) under different condition (concentration of sulfuric acid, concentration of chloride ions in solution and the surface of samples was clean or not) . The fastest measured corrosion rate was 14.45 mpy. After calculating with this result, it takes at least 1.24 years to completely dissolve the ammunition shell. Except for the high time costs, only relying on the corrosion rate to estimate cannot guarantee the actual treatment effect. In order to reduce the processing time, Faraday's laws of electrolysis is led, let brass be electrolytic dissolved in the electrolyte (sulfuric acid). The operating parameters are operating current, concentration of sulfuric acid and the chloride ions concentration. The experimental results indicate that the parameter which actually leads electrolysis reaction's rate is the operating current. However, when the current density on the surface of the sample is increased to a degree, the metal surface may be attached metal oxides to passivate, anode passivation may interfere with the electrolysis reaction. Anode passivation is a commonly used anticorrosive technology, but it has a negative impact on the electrolytic treatment process of this study. Therefore, using chronopotentiometry (CP) method to observe the anode passivation situation with a high current density of 200 mA/cm2 in 90 minutes. The operating parameter of this part are concentration of sulfuric acid, the chloride ions concentration and electrolyte condition (mixed or stable). The experimental result show that stirring electrolyte with magnet can almost avoid the anode passivation during brass electrolysis, and in the 1M sulfuric acid without stirring had the most obvious passivation situation. Therefore, add chloride ions in 1M stable sulfuric acid to delay the passivation time. The passivation time of 0 ppm, 30 ppm, 60 ppm, 90 ppm are 5.4, 4.2, 6.3, 9.0 minutes, can slightly delay the occurrence of passivation.