ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2025 27 recommending tensile and hydrogen- embrittlement proof testing (200 hours) of some of these bolts before further flight operations. An RNLAF crisis management team (CMT) promptly grounded all 33 aircraft and requested the NLR to devise and conduct a validation test program to quickly restore their operational readiness. The validation program began on July 6, 2007 and included the following steps: (1) relevance of proof testing; (2) tensile tests and fractography; statistical analysis of test data; and (3) electrochemistry and hydrogen diffusivity issues[13]. 1. Proof testing was considered unnecessary, based on classic literature data and the suspect bolts having survived much longer than 200 hours in the assembled, fully torqued, and operational condition since nonapproved cleaning. 2. Tensile tests, fractography, and statistical analyses on 160 suspect bolts from five aircraft showed no evidence of strength deterioration or hydrogen embrittlement. 3. An ad hoc Pourbaix diagram indicated that at the pH level of the paint stripper used on the originally cadmium-plated bolts it might have been possible for hydrogen to be absorbed by the bolts. However, the bolts would not have corroded during this treatment. Also, after removal from the paint stripper the maximum time any hydrogen could have remained in the bolts would have been less than eight days[13]. This was much less than the time before reinstallation into the WAF bolt assemblies (i.e., 3-4 weeks). The results of the validation program were officially reported to the RNLAF CMT on July 13, 2007. The CMT decided that the grounded aircraft could be cleared for further operation after the remaining (complete) WAF bolt assemblies were cleaned and coated with primer. These assemblies were then to be replaced no later than during the next scheduled inspections. Replacement bolts (160) were installed on the other five aircraft. SUMMARY Forensic metallurgy in archaeology and aerospace engineering follows similar principles but has different starting points and goals. Archaeometallurgy is concerned with acquiring scientific knowledge about artifacts, the historical and cultural aspects of provenance, and optimizing conservation. Forensic aerospace investigations are primarily concerned with failure analyses of components, the physical causes, and root causes such as inadequate engineering knowledge, incorrect assumptions about service operational conditions, and errors in manufacturing and maintenance. In both cases, forensic metallurgy—and other forensic disciplines—rely on teamwork. ~AM&P For more information: Russell Wanhill, emeritus principal research scientist, Aerospace Vehicles Division, Royal Netherlands Aerospace Centre, rjhwanhill@gmail.com. References 1. H.J. Plenderleith, The Conservation of Antiquities and Works of Art: Treatment, Repair, and Restoration, Oxford University Press, London, 1956. 2. R.M. Organ, The Current Status of the Treatment of Corroded Metal Artifacts, in B.F. Brown, et al (Eds.), Corrosion and Metal Artifacts ‒ A Dialogue Between Conservators and Archaeologists and Corrosion Scientists, National Bureau of Standards, Special Publication 479, Washington, D.C., p 107-142, 1977. 3. A. Giumlia-Mair, The Enkomi Cup: Niello versus Kuwano, in V. Kassianidou and G. Papasavvas (Eds.), Eastern Mediterranean Metallurgy and Metal- work in the Second Millennium BC, A Conference in Honour of James D. Muhly, Nicosia, October 10-11, 2009, Oxbow Books, Oxford, p 107-116, 2012. 4. R.J.H. Wanhill and A. Giumlia-Mair, The Enkomi Cup: Macrophotographic Damage Assessment, Historical Metallurgy, 54(1), p 1-8, 2022. 5. R.J.H. Wanhill, Stress Corrosion Cracking in Ancient Silver, Stud. Conserv., 58(1), p 41-59, 2013. Fig. 5 — Schematic of some of the upper WAF assemblies on an F-16 wing[13]. GET ENGAGED, GET INVOLVED, GET CONNECTED The ASM Archaeometallurgy Committee is an active group of ASM members with interest and experience in the study and characterization of historic metals and artifacts. Committee projects include developing a special journal issue and organizing IMAT conference programming. Members with similar interests are welcome to join. For more information, contact staff liaison Scott Henry, scott.henry@asminternational.org.
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