Investigating the tarnish and corrosion mechanisms of Chinese gold coins

2011 ◽  
Vol 43 (4) ◽  
pp. 763-769 ◽  
Author(s):  
Chenghao Liang ◽  
Changjiang Yang ◽  
Naibao Huang
Author(s):  
Svante Fischer

In this paper, I discuss the context of a Late Roman solidus hoard found in the Casa delle Vestali on the Forum Romanum in Rome. The hoard consists of 397 solidi, Late Roman gold coins. Most of the hoard consists of uncirculated solidi struck in the name of the Western Roman emperor Procopius Anthemius (AD 467–472). By means of situating the hoard within the context of the reign of Anthemius and the collapse of the Western Roman Empire, the aim of this paper is to determine if the coins in the Vestal hoard can be related to other contemporary coin hoards by means of numismatic typology; this information could add to our understanding of why Anthemius’ reign is considered such an unmitigated failure and why the Empire collapsed soon after his murder. In this article, the composition of the hoard is examined, and the contents are compared to other contemporary solidus hoards in the Mediterranean, Gaul, Poland and Scandinavia. I argue that this comparison shows that the Vestal hoard is not part of a larger network but that the hoard constitutes the remains of an isolated occurrence—as initially suggested by its unusual composition and location.


1989 ◽  
Vol 6 (31) ◽  
pp. 145-182
Author(s):  
Mando Caramessini-Oeconomides ◽  
Phane Drossoyianni
Keyword(s):  

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3563
Author(s):  
Mathieu Robineau ◽  
Valérie Deydier ◽  
Didier Crusset ◽  
Alexandre Bellefleur ◽  
Delphine Neff ◽  
...  

Carbon steel coupons were buried in a specific low-pH cement grout designed for radioactive waste disposal and left 6 months in anoxic conditions at 80 °C. The corrosion product layers were analyzed by µ-Raman spectroscopy, XRD, and SEM. They proved to be mainly composed of iron sulfides, with magnetite as a minor phase, mixed with components of the grout. Average corrosion rates were estimated by weight loss measurements between 3 and 6 µm yr−1. Corrosion profiles revealed local degradations with a depth up to 10 µm. It is assumed that the heterogeneity of the corrosion product layer, mainly composed of conductive compounds (FeS, Fe3S4, and Fe3O4), promotes the persistence of corrosion cells that may lead to locally aggravated degradations of the metal. New cement grouts, characterized by a slightly higher pH and a lower sulfide concentration, should then be designed for the considered application.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hailong Dai ◽  
Shouwen Shi ◽  
Lin Yang ◽  
Can Guo ◽  
Xu Chen

Abstract Hydrofluoric acid (HF) or fluoride ion corrosion issues are often encountered in many fields, which have attracted extensive research due to its strong corrosiveness. In this paper, a critical review is presented based on recent progress on HF corrosion. In view of the discrepancy of fluoride ion compared with other ions, the special attack characteristics of fluoride ion are firstly discussed. Afterwards, the corrosion mechanisms of stainless steels, nickel-based alloys, and titanium alloys in HF solution or fluoride ion-containing environment are reviewed, and three typical corrosion behaviors are summarized, which are essentially weakening process of passivation of metallic materials. The effects of influencing factors (e.g. alloying elements, environmental factors, and stress, etc.) on HF corrosion are also discussed, which involve changes in passivation mechanism, the influence of HF attack mode and multiple damage mechanisms due to mechanical–chemical coupling. Finally, future research works on HF corrosion are proposed.


2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Hao-Hsiang Huang ◽  
Fan-Bean Wu ◽  
Jyh-Wei Lee ◽  
Li-Chun Chang

The Ni-alloy/CrN nanolayered coatings, Ni-Al/CrN and Ni-P/CrN, were deposited on (100) silicon wafer and AISI 420 stainless steel substrates by dual-gun sputtering technique. The influences of the layer microstructure on corrosion behavior of the nanolayered thin films were investigated. The bilayer thickness was controlled approximately 10 nm with a total coating thickness of . The single-layer Ni-alloy and CrN coatings deposited at were also evaluated for comparison. Through phase identification, phases of Ni-P and Ni-Al compounds were observed in the single Ni-alloy layers. On the other hand, the nanolayered Ni-P/CrN and Ni-Al/CrN coatings showed an amorphous/nanocrystalline microstructure. The precipitation of Ni-Al and Ni-P intermetallic compounds was suppressed by the nanolayered configuration of Ni-alloy/CrN coatings. Through Tafel analysis, the and values ranged from –0.64 to –0.33 V and to  A/, respectively, were deduced for various coating assemblies. The corrosion mechanisms and related behaviors of the coatings were compared. The coatings with a nanolayered Ni-alloy/CrN configuration exhibited a superior corrosion resistance to single-layer alloy or nitride coatings.


2010 ◽  
Vol 52 (2) ◽  
pp. 562-578 ◽  
Author(s):  
Ming Liu ◽  
Patrik Schmutz ◽  
Sandrine Zanna ◽  
Antoine Seyeux ◽  
Helene Ardelean ◽  
...  

1951 ◽  
Vol 16 (2) ◽  
pp. 41
Author(s):  
E. S. G. Robinson
Keyword(s):  

2021 ◽  
Vol 21 (4) ◽  
pp. 2221-2233
Author(s):  
Yaru Liu ◽  
Qinglin Pan ◽  
Xiangdong Wang ◽  
Ye Ji ◽  
Qicheng Liu ◽  
...  

The corrosion mechanisms for different corrosive media on the aged 7A46 aluminum alloy were systematically investigated at nanoscale level. The combination of empirical intergranular and exfoliation corrosion behavior was employed, and coupled with first-principles calculations. Results revealed that the dispersed distribution of matrix precipitates (MPs) leads to the enhancement of the corrosion resistance pre-ageing (PA) followed by double-ageing (PA-DA) alloy. The deepest corrosion depth of PA-DA alloy was in hydrochloric acid, and the calculation result demonstrates that the passivation effect in combination with the accumulation of corrosion products in nitric acid protect the PA-DA alloy from further corrosion.


ITNOW ◽  
2021 ◽  
Vol 63 (3) ◽  
pp. 6-7
Author(s):  

Abstract The BCS Financial Services Specialist Group compresses over 2,000 years of history and explains how we moved from using gold coins to being on the brink of governments issuing their own central bank digital currencies.


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