Abstract：
Engine numbers, which involve information regarding the engine type, production number, and year and place of manufacture, are used for identification purposes. Comprising of unique alphanumeric characters, the engine numbers are fully or partially obliterated especially in auto theft and smuggling cases to conceal the origin, identity, and owner of vehicles. The limitations of the current restoration techniques such as the difficulty of using chemical liquid etching in vertical sites, the restrictions of magnetic and optical methods, and the applicability of several techniques like electron backscatter diffraction only in the laboratory environment prompt the development of new techniques. In view of these limitations and the importance of restoring engine numbers in criminal investigations, this unique study aimed to develop an etching paste that would restore the effaced characters on a real aluminum alloy engine block. The characters which were cold-stamped on the engine block were milled at varying depths and restoration attempts were conducted using etching pastes formed with different chemicals and materials. The analyses indicate that the etching paste formed with 200 mg of perlite, 400 mg of iron powder, and 450 μL of 20 M NaOH provided restoration to a good extent. The prevention of over-etching through the controlling of the chemical reaction and the cost-effectiveness appears to be the advantages of this technique. The success of recovery on the real engine block, the facilitation of restoration on curved surfaces, and the chance of on-site usage will likely make the etching paste a widely used tool in serial number restoration.
摘要：
发动机编号,其中涉及有关发动机类型的信息，生产编号,制造年份和地点，用于识别目的。由唯一的字母数字字符组成，特别是在汽车盗窃和走私案件中，发动机数量被全部或部分删除以掩盖来源，身份，和车辆的所有者。当前修复技术的局限性，例如在垂直位置使用化学液体蚀刻的难度，磁性和光学方法的限制，电子背散射衍射等几种技术仅在实验室环境中的适用性促进了新技术的发展。鉴于这些限制以及在刑事调查中恢复引擎数量的重要性，这项独特的研究旨在开发一种蚀刻膏，可以恢复真正的铝合金发动机缸体上的磨损特征。在发动机缸体上冷冲压的字符在不同的深度下铣削，并使用由不同化学物质和材料形成的蚀刻膏进行修复尝试。分析表明，用200毫克珍珠岩形成的蚀刻膏，400毫克铁粉，和450μL的20MNaOH提供了良好程度的恢复。通过控制化学反应和成本效益来防止过度蚀刻似乎是该技术的优点。在真正的发动机缸体上成功回收，促进曲面上的修复，现场使用的机会可能会使蚀刻膏成为序列号恢复中广泛使用的工具。
