Forensic Science Programme, School of Health Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia.
Forensic Sci Int. 2010 Feb 25;195(1-3):86-92. doi: 10.1016/j.forsciint.2009.11.018.
Restoration of obliterated engraved marks on high strength Al-Zn-Mg-Cu alloy (AA7010) surfaces by etching technique was studied. The alloy surfaces were mechanically engraved with some identification marks using "Gravograph". The marks were then erased by removing the metal to different levels up to and below the depth of engraving. Five metallographic reagents were tested on the obliterated surfaces by etching. The following two methods (i) immersion in 10% aq. phosphoric acid and (ii) alternate swabbing of 60% HCl and 40% NaOH were found to be quite effective to reveal the obliterated marks. These two procedures were also able to show effectively the marks obliterated by over-engraving and centre punching. Of the two techniques immersion in phosphoric acid provided more contrast. Interestingly, alternate swabbing of 60% HCl and 40% NaOH presented itself to be the common reagent for restoration on pure aluminium as well as its alloy surfaces. This is evident from our own current experiments and those of earlier researchers [G. Peeler, S. Gutowski, H. Wrobel, G. Dower, The restoration of impressed characters on aluminium alloy motor cycle frames, J. Forensic Ident. 58 (1) (2008) 27-32; M. Izhar M. Baharum, R. Kuppuswamy, A.A. Rahman, Restoration of engraved marks on aluminium surfaces by etching technique, Forensic Sci. Int. 177 (2008) 221-227]. The findings have assumed importance as engines and chassis of cars and frames of firearms are currently made of high strength aluminium alloys and recovery on these surfaces by current methods is not satisfactory.
研究了通过蚀刻技术恢复高强度 Al-Zn-Mg-Cu 合金（AA7010）表面已磨灭的雕刻标记。使用“Gravograph”机械地在合金表面上刻划一些识别标记。然后通过去除金属来消除标记，直到达到和低于雕刻深度的不同水平。在被磨灭的表面上测试了五种金相试剂的蚀刻效果。发现以下两种方法（i）浸入 10%的 aq.磷酸和（ii）交替擦拭 60%HCl 和 40%NaOH 非常有效，可以揭示被磨灭的标记。这两种方法也能够有效地显示因过度雕刻和中心打孔而磨灭的标记。这两种技术中，浸入磷酸提供了更多的对比度。有趣的是，交替擦拭 60%HCl 和 40%NaOH 似乎是恢复纯铝及其合金表面上的标记的通用试剂。这一点从我们自己目前的实验以及早期研究人员的实验中可以看出[G. Peeler, S. Gutowski, H. Wrobel, G. Dower, 恢复摩托车车架铝合金上的印记字符, J. 法医鉴定 58 (1) (2008) 27-32; M. Izhar M. Baharum, R. Kuppuswamy, A.A. Rahman, 用蚀刻技术恢复铝表面的雕刻标记, 法医学 177 (2008) 221-227]。由于汽车的发动机和底盘以及枪支的框架目前都由高强度铝合金制成，而当前的方法在这些表面上的恢复效果并不令人满意，因此这些发现具有重要意义。
