Institute of Sciences, Forensic Science Division, Hacettepe University, Ankara, Turkey.
Department of Chemistry, Hacettepe University, Ankara, Turkey.
J Forensic Sci. 2023 Jul;68(4):1325-1329. doi: 10.1111/1556-4029.15303. Epub 2023 Jun 2.
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.
发动机号码包含有关发动机类型、生产编号以及生产日期和地点的信息，用于识别目的。由独特的字母数字字符组成，发动机号码被完全或部分抹去，特别是在汽车盗窃和走私案件中，以隐藏车辆的来源、身份和所有者。当前的恢复技术存在局限性，例如在垂直位置使用化学液体蚀刻的困难、磁性和光学方法的限制，以及电子背散射衍射等几种技术仅在实验室环境下的适用性，这促使新技术的发展。鉴于这些限制以及在刑事调查中恢复发动机号码的重要性，这项独特的研究旨在开发一种能够恢复真实铝合金发动机缸体上已磨损字符的蚀刻膏。在发动机缸体上冷冲压的字符被铣削到不同的深度，并使用由不同化学物质和材料制成的蚀刻膏进行了恢复尝试。分析表明，由 200mg 珍珠岩、400mg 铁粉和 450μL 20M NaOH 组成的蚀刻膏在很大程度上提供了恢复。通过控制化学反应，可以防止过度蚀刻，而且这种技术具有成本效益，这似乎是它的优势。在真实发动机缸体上成功恢复、在曲面恢复上的便利性以及现场使用的机会，很可能使蚀刻膏成为序列号恢复中广泛使用的工具。
