Showing 10 results for Corrosion
Hamidreza Bakhshandehfard, Sedighe Taheri,
Volume 1, Issue 1 (4-2017)
Abstract
The objects of the study are two bronze daggers dated back to the late Bronze Age and early Iron Age. They lack any ornaments and there is corrosion and oxidation in their surface. The purpose of this study is to recognize the technological and pathological research on the mentioned objects through comparative and pathological studies and library method, to conduct the technological and pathological research through laboratory method (wet chemistry, radiography, metallography, metal core elemental analysis by Scanning Electron Microscope (SEM), analysis of corrosion by X-ray diffraction (XRD) in order to identify the metal and making techniques and to determine the types of damage, and finally to perform the conservation and restoration of the these objects through the conservation plan.
After studying and conducting experiments mentioned, it was determined that the material of the objects was bronze with carbonate and chloride corrosion. The making methods in these objects is casting and hammering. They were recognized to belong to the Iron Age.
Parastou Naeimi Taraei, Shaiba Khadir,
Volume 1, Issue 1 (4-2017)
Abstract
Due to the complex corrosion mechanism of the bronze objects, explaining the structure of different layers of corrosion in these objects at microscopic levels is possible. Typically copper oxide(I) is the first corrosion layer on surface of bronze objects that are excavated of historical sites. However, depending on the environmental conditions، various forms of corrosion layer of tin or copper-rich oxide are formed that are effective in corrosion resistance of objects. Identification of tin oxides or copper-tin corrosion products is not simple by using of routine methods of instrumental analysis.However in this research the formation process of copper and tin oxides of some of historical bronze objects of Iran were studied by using the optical microscope with polarized light that show colored corrosion products and in some cases the method of scanning electron microscopy equipped with elemental analysis (SEM-EDX) was used to complete the identification process of oxide layers. According to the results, identify of evidence of differences in distribution of copper and tin in the microstructure that is result of macroscopic and microscopic segregation, formation of a solid solution of copper besides the copper-copper oxide eutectic mixture during the solidification process, the appearance of copper oxide inclusions in the microstructure of metal, moving The tin-rich layer of copper oxide layer to the outside, formation of copper oxide-tin oxide sandwiching layers, selective dissolution of tin in the outer layers, decuprification phenomenon in corrosion layers and condensation of tin oxides in the center of sample and finally the usual formation or degradation of copper oxide layer under certain conditions have been studied with microscopic imagesof selected samples of bronze objects which confirmed the ability of microscopic techniques in the study of oxide layers of bronze objects.
Shaiba Khadir, Parastoo Naeimi Taraei,
Volume 1, Issue 2 (10-2017)
Abstract
Given the nature of the chloride ion and its tendency to penetrate the inner layers of the metal, paying attention to it in the field of protection of metal artifacts is of great importance. In this article, the effect of the attacking chloride ion on historical copper and silver-based metals has been discussed, and according to the results of a long-term research project on the pathology of metal artifacts in Iran, various examples of artifacts affected by chloride attacks have been briefly presented and compared. In conducting corrosion studies in the aforementioned project, X-ray imaging, optical microscopy, and scanning electron microscopy, and wet and instrumental analysis methods (EDX, XRD, PIXE) were used to analyze the corrosion process. According to the studies conducted, severe pitting corrosion with progressive conditions was observed in the works of the Rasht Museum, as well as corrosion of the tin-rich phase and its simultaneous release as oxide compounds in many of the mirrors in this museum, which in many cases had a starting point under surface sediments when local conditions were provided. This process in the works in museums in southern Iran with high humidity conditions and with chlorides concentrated in the corrosion products has caused the loss of the metal core in many of the works obtained from Hormuz. The concentration and crystallization of chloride in the corrosion layers and the attacks caused by it in the works of the dry regions of Iran, despite periodic humidity or uncontrolled storage conditions after excavation, is the cause of the loss of the metal core of many of the works obtained from Sites such as Sarm, Qoli Darvish, and Sialk have been affected by chloride attacks through different mechanisms, from chloride penetration into the oxide layer to the dissolution and removal of copper from the outer layers. Silver artifacts obtained from different sites have also been affected by chloride attacks, due to the presence of horn silver chloride compounds (Sialk), severe local corrosion (Hormoz), and intermittent copper deposition and the deposition of its chloride salts (Teppeh-e-Hisar).
Mohammad Mortazavi, Ahmad Salehi Kakhki , Mohammad Ali Golozar , Hassan Tala’i ,
Volume 1, Issue 2 (7-2017)
Abstract
One of the most widely used terms in the conservation and restoration of cultural and historical artifacts, particularly in the field of ancient metal objects, is patina. Although, this term is also applied to other historical materials, such as paintings and stones, its frequent used in the context of ancient bronzes makes it essential to develop a clear and accurate understanding of its meaning and implications. From the perspective of the studying deterioration of the artifacts, patina-as corrosion products in bronze artifacts-can significantly impact both the tangible and intangible aspects of the objects. on the one hand, it contributes certain values, such as age and aesthetics. On the other hand, it serves as an important criterion in conservation and restoration practices. However, the lack of comprehensive and precise definition of this term leads to complexity in conservation decision-making. In this paper, based on a literature review, the differing and similarity viewpoints on patina have been investigated. Following this, the term is reviewed in relation to different corrosion morphologies, and issue related to its current definitions are discussed. The different values of the patina are debated, and its role in the principles of conservation is reevaluated. In this field, confusion arising from the application of the term patina in the conservation of archaeological bronzes have been highlighted. Finally, considering the unique properties of corrosion phenomena in archaeological bronzes, the concept of the “original surface” is discussed as an approach to addressing this issue.
Hamidreza Bakhshandeh-Fard,
Volume 1, Issue 2 (7-2017)
Abstract
Conservation science is an interdisciplinary field that largely owes its foundation to other sciences. Among these sciences, electrochemical methods can be mentioned. Electrochemical methods play an important role in various aspects of the conservation and restoration of historical objects. Briefly, the application scope of electrochemical methods in conservation and restoration can be divided into: identification and investigation of constituent materials in historical artifacts, restoration and cleaning methods, and environmental condition assessments in museum display areas and storage facilities of historical objects. Identification and Investigation of Constituent Materials: Identifying the components of artistic and archaeological artifacts is an important matter in scientific investigations. Some of these objects are composite. Additionally, some objects are heterogeneous while others are homogeneous, and some are accompanied by considerable amounts of other materials, such as binding media, paints, pigments, etc. At first glance, it may seem that electrochemical methods could perform this task without causing damage to the artifact. However, further investigations in this area are required. Restoration and Cleaning Methods: Electrochemistry has been used for over a century in the treatment of historical metal objects. These methods can be employed in artifact treatment; perhaps their ideal capability would be reversing the corrosion process in ionic compounds. However, in applying these methods, depending on the condition of the artifact, treatment priorities may lean toward strengthening, stabilization, or cleaning of the historical artifact. Environmental Condition Assessments: Scientists and researchers are continuously investigating and evaluating harmful conditions in museum environments. This is because pollutants, even in very small quantities, can be one of the most important factors in the deterioration of historical artifacts, and their detection and identification are often inaccessible due to high sensitivity and cost. Moreover, conventional methods lead to the identification of pollutants at low concentrations (one part per billion), but it is difficult to determine their damage potential. This is because the synergistic effects (Synergy) and additive effects of these compounds when mixed together, as well as their surface effects on historical objects, cannot be accurately calculated. Can electrochemical methods be used as a measurement tool for investigating museum conditions? This paper generally addresses the role, importance, strengths, and weaknesses of electrochemical methods in the aforementioned areas within the field of conservation and restoration of historical objects. The aim of this paper is to present a new approach to the application of electrochemical methods and their advantages and disadvantages in the restoration and conservation of historical artifacts.
Narges Doosti Sani, Mahshid Ilkhani, Shaiba Khadir, Afshin Ebrahimi,
Volume 2, Issue 1 (6-2019)
Abstract
The study of metal works of Bam citadel (Arg-e-Bam) is underway to study the pathology of metalworks in Iran.The aim of this project is to study and investigate the corrosion mechanisms of metal objects. Various metallic works including iron, silver and copper alloys have been gained from the area of Arg-e-Bam. The research is focused on a number of bronze works of this historical site.The studies have been done using Microscopic and Macroscopic methods including metallography, wet chemistry, X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). According to dendritic structure of these objects, the results show that most of them have been made in casting method and corrosion products are including Cuprite (Cu2O), Azurite (Cu3(CO3)2(OH)2), Brochantite (Cu4(OH)6SO4), Cassiterite (SnO) and the chloride compounds like Atacamite (Cu2Cl(OH)3), Paratacamite (Cu2Cl(OH)3, Nantokite (CuCl) and Melanothallite (Cu2OCl2). The noticeable point is that there are inclusions containing iron and sulfur in all specimens that represent the using of sulfide ore in copper extraction process.
Parastoo Naeimi Taraei, Seyed Mohammad Amin Emami, Abolghasem Dolati,
Volume 2, Issue 2 (9-2019)
Abstract
Various chemical and natural substances have been employed to control corrosion in historical metal artifacts. However, the use of these substances has not always been effective and has occasionally led to secondary issues. This article reviews the existing challenges associated with corrosion inhibitors and investigates factors influencing the selection of materials to optimize corrosion control conditions. Based on available data, a multifunctional derivative of phosphonic acid with active phosphorus and nitrogen centers was selected. Its effectiveness in controlling corrosion of iron artifacts was evaluated through electrochemical impedance and polarization measurements, as well as microscopic methods. The results demonstrate the material’s ability to reduce corrosion rates at very low concentrations with minimal impact on the artifacts’ appearance, marking a significant step toward their preservation. Furthermore, the potential for optimizing corrosion control conditions through the use of complementary materials alongside phosphonic acid derivatives, leveraging their synergistic effects, is discussed.
Shaiba Khadir, Fathollah Niyazi, Kouorsh Kouhestani,
Volume 6, Issue 4 (3-2024)
Abstract
The "Clogs of the Kaaba" at the Iran Carpet Museum is a pair of metal/ copper alloy shoes by Parviz Tanavoli for an outdoor installation. The work is part of a memorial chapel designed minimalist style within the museum’s grounds. The clogs are crafted to a life-size scale, with their surfaces textured with fine and delicate grooves to enhance their aesthetic and visual appeal. The artist has also applied a dark artistic patina to the surface of the clogs. The interior of the clogs has accumulated dust, soot, and debris from the surrounding greenery. Additionally, prolonged exposure to environmental conditions such as annual rainfall, seasonal temperature variations, and urban pollutants such as acid rain has affected their condition on the ground. The surface of the clogs shows green corrosion products and carbonate deposits. the aim of this operation is to stabilize the clogs and prevent further exposure to harmful urban environmental factors. In order to evaluate and document the current condition, digital photography was conducted on both a macroscopic and microscopic scales. Surface sediment removal was carried out using manual mechanical methods with a scalpel and ultrasonic device. The poultice method was applied in a controlled and limited manner to remove thick sediments using Rachel's salt solution and%2 hydrochloric acid. To protect the surface, a %3 BTA (benzotiazol: C6H5N3) solution was used, followed by a coating of epoxy polyamide solution.
Fatemeh Alamirzaei, Parasto Naeimi Taraei,
Volume 7, Issue 3 (11-2024)
Abstract
The study of corrosion mechanisms in ancient bronze artifacts, particularly those from the salty and humid region of Hormuz, is crucial due to severe corrosion. This article examines a bronze dagger attributed to excavations in Hormuz to analyze its corrosion behavior influenced by the environment. Techniques such as X-ray imaging, stereomicroscopy, X-ray diffraction (XRD), polarized light microscopy (PLM), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) were employed. Results show that most of the dagger has transformed into corrosion products, including copper and tin oxides, as well as basic chloride compounds like atacamite and paratacamite, forming a three-layered corrosion structure. The corrosion mechanism involves selective dissolution of copper, its migration to outer layers, and the concentration of tin oxide compounds in the central regions, accompanied by chloride ion penetration. This process has preserved patterns of grain structure and thermal twinning in the inner oxide layers, with periodic deposition of copper and tin oxides indicating the formation of a colloidal solution of copper and tin salts beneath the soil (Scott, 2002; Robbiola et al., 1998).
Elaheh Hajjari, Mohammad Mortazavi, Keyvan Raeissi, Mohammad Hafezi Kahnamoei ,
Volume 8, Issue 4 (3-2026)
Abstract
The inherent instability of archaeological iron objects is due to contaminated with chloride ions from the burial environment, as well as being exposed to oxygen and high relative humidity. Therefore, the removal of chloride ions and the stabilization of active corrosion are essential steps to prevent further deterioration and to preserve these artefacts. Numerous scholars have investigated various methods for the dechlorination of archaeological irons. However, the complexity of the corrosion mechanisms, the varying condition under which artefacts were buried, the specific characteristic of each object, and the ethical principles of conservation and restoration confront conservation scientists with significant challenges. As a result, from the earliest research in this field to the present day, studies in the subjects are still ongoing. A meticulous review of the literature can lead to a better understanding of existing research findings and help identify aspects that more research is needed. The aim of this paper is to review, critique and examine each of the different chlorination methods, while also discussing their disadvantages and limitations. This review discuses different methods of chloride ions removal and stabilization of archaeological iron artefacts, including electrochemical techniques, immersion in alkaline aqueous solutions, application of subcritical fluids, hydrogen plasma, and biological treatment using bacteria. In addition, factors affecting the process before, during, and after dechlorination, as well as the specific challenges of treating large and composite objects are examined. Finally, by reviewing and comparing the studies conducted in this paper, it was found that there are still gaps in this regard, the analysis of which will ultimately lead to the application and optimization of appropriate dechlorination methods tailored to the specific characteristics of each object and its conservation conditions.
