Managing a Monitor — the Case of HMVS Cerberus in Port Phillip Bay: Integration of Corrosion Measurements with Site Management Strategies

Abstract

The hull of the former HMVS Cerberus (1926) collapsed two metres during gales in December 1993, leaving the vessel half-submerged. Sunk as a breakwater in 1926, the vessel is one of the few remaining and accessible twin-turret Monitor-style warships from the 1870s. This paper presents the complex history of attempts to stabilize the site and to preserve the wreck. A series of in situ corrosion studies of corrosion potentials, pH, and residual metal thickness have provided a special insight into the processes of decay and have paved the way for future site stabilization. Removal of the four 16-tonne 10 inch Armstrong rifled muzzle loading guns and their in situ treatment alongside the wreck have assisted in relieving some of the stress on the remaining structure. The paper reports on correlations between the corrosion rate and the formation of concretions and how to determine the end point of an in situ treatment for cannon.     

5,000 years old Egyptian iron beads made from hammered meteoritic iron

The earliest known iron artefacts are nine small beads securely dated to circa 3200 BC, from two burials in Gerzeh, northern Egypt. We show that these beads were made from meteoritic iron, and shaped by careful hammering the metal into thin sheets before rolling them into tubes. The study demonstrates the ability of neutron and X-ray methods to determine the nature of the material even after complete corrosion of the iron metal. The iron beads were strung into a necklace together with other exotic minerals such as lapis lazuli, gold and carnelian, revealing the status of meteoritic iron as a special material on a par with precious metal and gem stones. The results confirm that already in the fourth millennium BC metalworkers had mastered the smithing of meteoritic iron, an iron–nickel alloy much harder and more brittle than the more commonly worked copper. This is of wider significance as it demonstrates that metalworkers had already nearly two millennia of experience to hot-work meteoritic iron when iron smelting was introduced. This knowledge was essential for the development of iron smelting, which produced metal in a solid state process and hence depended on this ability in order to replace copper and bronze as the main utilitarian metals.     

Magnetic properties of ancient coins

The almost ubiquitous presence of small amounts of iron in ancient coins gives them remanent magnetic properties which can be measured easily on commercial magnetometers. The stability of the remanence suggests that ancient coins might retain information about the geomagnetic field at the time and location of manufacture and so be valuable in setting up archaeomagnetic dating curves. However, measurements show that the remanence directions tend to be too scattered for this purpose, although it is quite possible to distinguish magnetically the obverse and reverse faces of struck coins.Saturation remanence studies of coins and coin analogues indicate that the main carrier of the remanence in struck coins is precipitated fine-grained iron (rather than the oxides of iron) which is produced during the minting process. The intensity of the remanence generated depends upon the thermo-mechanical history of the flan prior to striking, which suggests that the magnetic properties of such coins are not simply related to the provenance of the ores used.     

The Thaikkal-Kadakkarappally Boat: an Archaeological Example of Medieval Shipbuilding in the Western Indian Ocean

Recent excavations at Kadakkarappally in Kerala, south-west India, have unearthed the remains of an iron-fastened boat, believed to predate the earliest known records for the use of iron in South Asian boatbuilding. The design departs significantly from the traditional view of Indian watercraft, although the use of locally available timber and the suitability of the design for use in the backwaters that characterise the region suggest that it was built and used in India. This is the first excavation of its type to take place in Kerala and contradicts the belief, widely held in Kerala, that the survival of organic remains has been negated by the tropical climate of the region.
© 2004 The Nautical Archaeology Society     

A technological transition in Mongolia evident in microstructure,chemical composition and radiocarbon age of cast iron artifacts

Metallurgical examination of cast iron objects from the Khitan period (AD 10th–12th) in Mongolia shows that they might be classified into two groups. The first is based on Fe–C alloys of near eutectic composition and the second is based on Fe–C–Si alloys with reduced carbon content and numerous sulfide inclusions. By contrast, all the objects from the succeeding Mongolian empire period (AD 12th–15th) belong to the second group, indicating that a technological transition had occurred during the Khitan period. Accelerator mass spectrometry (AMS) on carbon samples extracted from artifacts in both groups and measurement of alloy compositions suggest that the use of mineral coal in smelting was a major factor for this transition.     

铁器文物腐蚀与保护的研究现状

影响铁器文物腐蚀的主要因素有氧化气氛、潮湿环境、土壤的酸碱性环境和可溶性环境.本文介绍了铁器腐蚀的主要产物以及研究铁器文物腐蚀的主要方法,综述了目前国内外对铁器文物腐蚀和保护研究的最新进展.     

Microstructural and elemental analyses of slags excavated from Xuxiebian iron‐smelting site,Sichuan, China

Xuxiebian is an iron‐smelting site located in Pujiang county of Sichuan province, China. Two excavations were carried out in 2007 and 2011, and four bowl‐shaped furnaces were excavated. Ten slag samples from the site were prepared and analysed. The present paper reports the results of metallographic and elemental examination of the specimens. It is concluded that both pig‐iron‐smelting and refining process were applied at the Xuxiebian site, and the bowl‐shaped furnaces are possibly refining furnaces. The function of the site was probably to produce pig iron and refine the pig iron into wrought iron.     

A Multidisciplinary Strategy for the Inspection of Historical Metallic Tie-Rods: The Milan Cathedral Case Study

A reliable assessment of historical metallic tie-rods requires both the estimation of actual tensile load and the identification of dominant defects. Despite high defectiveness resulting from traditional metalworking techniques, so far the latter aspect has not been duly addressed in the literature. In this article, several methodologies are discussed aimed at integrating the usual inspection practice. All studies were performed on the tie-rods of Milan Cathedral. Metallurgical analyses allowed to recognize the main features of the material. Mechanical characterization in the perspective of Elasto-Plastic Fracture Mechanics (EPFM) indicated the conditions for crack propagation. Several Non-Destructive Techniques (NDTs) commonly used in Mechanical Engineering (i.e., guided waves, eddy currents, pulsed active thermography) were examined and adapted to this unconventional application. Based on the combination of all the mentioned methods, a multidisciplinary procedure was defined, which allows the evaluation of the crack significance with reference to the estimated working stress.     

Mineralogical and Chemical Characterization of Roman Slag from the Archaeological Site of Castra (Ajdovščina,Slovenia)

This study deals with the mineralogical and chemical characterization of archaeometallurgical material from the Roman archaeological site of Castra (Ajdov??ina, western Slovenia). Samples were initially analysed via optical microscopy and X‐ray powder diffraction, with the composition of individual phases then determined using scanning electron microscopy coupled with electron‐dispersive spectroscopy, and Raman microspectroscopy. Chemical investigation was carried out by using inductively coupled plasma atomic emission spectroscopy to measure the major element content. The results showed that the slag originated from iron smithing operations, with calcium‐rich olivines, as well as wuestite and leucite, the most abundant phases. The investigated slags were also found to be characterized by significantly high lime levels, which probably promoted the formation of the calcium‐rich olivines.     

The Role of Pattern‐Welding in Historical Swords—Mechanical Testing of Materials Used in Their Manufacture

Pattern‐welding is a well‐known technique that was widely employed in the manufacture of swords. While the decorative effect of genuine pattern‐welding (employing phosphoric iron) is indisputable, to date its reinforcing effect is rather unclear. In order to understand this issue better, wrought iron, phosphoric iron, steel and various pattern‐welded samples were prepared and mechanically tested, and the results obtained are discussed in detail. Both the mechanical testing and the long‐term metallographic investigation of medieval swords suggest that pattern‐welding does not have any significant positive effect on the mechanical properties of swords and we should consider it a primarily decorative technique.