Voltammetric behaviour of an archeaological bronze alloy in aqueous chloride media

The interface archaeological bronze alloy‐chloride media was characterized by using linear sweep rate cyclic voltammetry. The electrochemical behaviour of the Cu‐Sn alloy being different from pure copper and pure tin. In fact, the voltammograms show an anodic peak and two cathodic peaks. Surface examination revealed a compact layer which spread over the ancient material. The influence of different parameters such as scan rate, chloride concentration and repetitive cycling on the voltammetric response of the archaeological bronze was also studied. The results indicate that patina layer formation is a spreading process over the electrode surface leaving only small pores. Diffusion of the halide controls the growing rate of this layer. Two other anodic peaks are evidences when potential cycling increases. The oxidation became more difficult as a result of a constant layer thickness.     

Comparaison between archaeological and artificially aged bronze interfaces

This paper establishes a comparison between the interface exhibited by an archaeological bronze alloy when previously submitted to a burial environment and a chloride electrolyte. The SEM‐EDAX analysis shows that the archaeological surface exhibited a three layered structure characterized by a tin enrichment at the inner layer, the succeeding layer being only by copper species, the outer layer is relevant of the burial environment. This corrosion structure is to be regarded as Type I morphology described in the literature for bronzes exhumed in the northern side of the Mediterranean Sea. When submitted to chloride solution, the open circuit potential of material tends to constant values after five days of immersion time. The evolution of the resulting interface was characterized using EIS and the spectra obtained were tentatively fitted using a simple electrical equivalent circuit. When, the interface attained the steady state, the interface shows a patina with two layered morphology similar to the archaeological one.     

The atmospheric corrosion of quaternary bronzes: The action of stagnant rain water

The corrosion behaviour of a quaternary bronze UNS C83600 exposed to stagnant acid rain was examined through wet-dry tests. During the tests, parallel monitoring was performed to determine the evolution of both the bronze surface and the weathering solution composition. The results show that the kinetics of bronze oxidation is governed by diffusion through a two-layer patina: an inner Sn-rich layer and an external Cu and Pb-rich layer. The corrosion rate of the alloy decreases with time, but the dissolution of individual metals (Cu, Zn and Pb) in the environment increases with different trends, showing progressive patina destabilisation.     

Assessment of the interphase behaviour of two bronze alloys in archaeological soil

The aim of this work is to evaluate the behaviour of bronze in archaeological soil by gravimetric study, electrochemical research and analytic survey. Archaeological soil samples were collected from Jama that date back to the second Punic war. Mineralogical, micro‐structural, micro‐morphological and chemical analyses of soil constituents were performed. The bronze samples correspond to Cu‐9.4Sn (B₁) and Cu‐7.7Sn with 1% of Pb (B₂). The open circuit potential value recorded for B₂/corrosion product/soil is stable after only 7 min due to its reactivity allowing to a rapid development of a protective corrosion layer. The B₂ interphase is more developed and stable than B₁. Under anodic polarisation, the B₂ alloy corrodes less than the B₁ alloy owing to its lower anodic current. Based on the EIS study, two evolution stages of the bronze alloy/corrosion product/soil interphase are detected. For the first stage, the interphase is equivalent to two R//C loops at high and medium frequencies, respectively related to the corrosion layer and charge transfer process, associated to mass transport phenomena. For the second stage, the resistance of corrosion layer decreases and the first loop vanishes. SEM‐EDS analysis demonstrate that the first stage (20 days of immersion) can be characterized by a well covered surface with a thin corrosion product, the external layer exhibits low tin content. However, after 310 days of immersion, the surface state is different with isolated particulates composed by Cu and soil compounds on a cracked layer with the presence of craters showing an internal layer.     

Long term corrosion behaviour of copper in soil: A study of archaeological analogues

The long term corrosion behaviour of copper in soil environment has been addressed by studying two archaeological copper samples. The microstructures of the material of construction of a Chalcolithic (2350BC‐1800BC) copper chisel from Balathal and an OCP period (2650BC‐800BC) Cu anthropomorphic object have been first characterized by microscopy and the features understood by stereological methods. The equiaxed grain size, coring effects in the grains and the relatively soft matrix of the OCP copper object indicated that it was manufactured by casting. The deformed grains near the surfaces and variation in the microhardness of the sample at different points suggests that the Chalcolithic copper chisel was processed by cold deformation after casting of the square cross section chisel. The surface patina on the two archaelogical copper objects has been characterized by X‐ray diffraction. In the case of OCP copper, the green surface patina was analyzed as a mixture composed mainly of cuprite, and minor amounts of malachite and brochantite. In the case of Chalcolithic copper, the patina was composed of sulfates and oxysulfates in the outer layers while the inner layers were rich in copper oxides. The electrochemical behaviour of both the archaeololgical coppers has been characterized and compared with that of a modern Cu sample by potentiodynamic polarization studies. The corrosion rate, determined by Tafel extrapolation technique in 3.5% NaCl solution, of Chalcolithic Cu was only marginally higher than that of modern and OCP Cu. The higher rates of corrosion in case of archaeological coppers have been attributed to the presence of second phase sulfide inclusions.     

带锈青铜表面超疏水薄膜的制备及防腐性能研究

目的 研究带Cu2O锈青铜表面超疏水薄膜的制备工艺及其防腐性能。方法 采用直接浸泡法,在带氧化亚铜锈层青铜试片表面制备了超疏水薄膜,通过单因素实验分别考察了正十二硫醇-十四酸混合溶液配比以及浸泡时间对超疏水膜层构建及耐蚀性能的影响,并采用接触角测试、电化学方法及表面分析手段对膜层性质、结构及稳定性进行了评价。结果 正十二硫醇和十四酸的疏水长链成功组装到带Cu2O锈青铜表面。混合溶液含5.0 nmol/L的正十二硫醇和1.0 nmol/L的十四酸,浸泡时间为1 h,是超疏水薄膜的最佳制备条件,此时表面接触角为157.2°,缓蚀效率高达97.21%。同时,电化学阻抗谱结果显示,电荷转移电阻相较于超疏水处理前增大了2个数量级,表明该膜层具有良好的耐蚀性能。该膜层在大气模拟液中浸泡30 d后,缓蚀效率仍有96.56%,说明其稳定性优异。结论 带Cu2O锈青铜表面构建的超疏水薄膜能够有效提高其耐腐蚀性和疏水性。     

苯并三唑对碳钢/铜合金电偶腐蚀行为的影响

目的 研究NaCl溶液中苯并三唑(BTA)对碳钢/铜合金电偶腐蚀行为的影响.方法 使用丝束电极(WBE)技术和电化学阻抗谱(EIS)技术研究在未添加和添加BTA的NaCl溶液中,丝束电极表面的电位分布、电流密度分布和电化学阻抗谱演化,同时对比分析碳钢区域与铜合金区域的阻抗谱特征.结果 在未添加BTA的条件下浸泡72 h...     

Pedological stratification effect of corrosion and contamination products on Byzantine bronze artefacts

Abstract

The present paper deals with the identification of six ancient Byzantine bronze coins found in the same archaeological site of Nufarul (Tulcea County, Romania), by corrosion product and alloy analysis. The microstratigraphies (i.e.layers), together with microchemical tests including reflection colorimetry, IR spectroscopy, X-ray diffraction and scanning electron microscopy assisted by X-ray spectrometry have rendered evident the stratified morphology of three types of patina. They are the primary type resulting from redox processes, the secondary type determined by acid–base and related hydrolytic processes and the ternary type (or the contamination patina) from segregation, diffusion and osmosis processes. The stratigraphical distribution of the chemical components in the structure of the patina is caused by the pedological (soil) processes at the archaeological sites and can be the main factor used in the authentication of ancient bronze artefacts.     

Characterization of corroded bronze Ding from the Yin Ruins of China

This paper presents the result of scientific examinations carried out on the soil-buried archaeological bronzes Ding from Yin Ruins of China. Eight of typical fragments from different bronze Ding were selected as researched samples according to their deterioration characteristics. Optical microscopy (OM), scanning electron microscopy coupled with energy (SEM-EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to understand the corrosive morphological characteristics, to clear the nature of patina and to analyze the elementary composition of bronze Ding. The results indicated that it is not possible to distinguish the original lustrous metallic surface in most samples because of the corrosive crust. The substrate of bronze Ding contains74-86% Cu, 1.1-4.6% Pb, and 10-18% Sn, which is in agreement with the historical investigation in the ritual vessels of Shang time. Copper-containing compounds were the main constituents of natural patina: Cu₂(OH)₃Cl existed as corrosion product in all the powdery or crack surface; Cu₂(OH)₂CO₃ was the main corrosive product in a compact and hard corrosive surface. This study provides useful information for the restoration and protection of bronze Ding in Yin Ruins.     

BTA缓蚀剂在文物保护中的应用

根据青铜器的腐蚀现象和文物保护的特殊要求,从苯骈三氮唑（ＢＴＡ）的化学作用机理及它对青铜保护的实际使用效果,讨论它在青铜器文物保护中的应用状况。     

Corrosion behaviour of bronze in urban environments: influence of tin content

Abstract

In this paper, the influence of the tin content on the corrosion behaviour of copper alloys was investigated. Three different bicomponent bronze alloys were exposed to a natural urban environment. The kinetic corrosion processes and the patina properties were monitored using the open circuit potential, electrochemical impedance spectroscopy and spectrocolorimetry. Results show that the bronze corrosion behaviour improves upon increasing the tin content. In addition, the mechanism of the patina formation is different for the three alloys.     

Corrosion behaviour of Cu-10Sn bronze in aerated NaCl aqueous media - Electrochemical investigation

Investigation of the electrochemical behaviour of Cu-10Sn (wt.%) alloy has been conducted in aerated aqueous chloride solutions and compared to that of pure Cu and Sn. Cathodic and anodic bronze behaviours have been investigated in function of the chloride concentrations (0.1-0.001 M), the rotation speed of the electrode and the potential sweep rate after 1-h immersion time in open-circuit conditions. At the corrosion potential, the corrosion behaviour appears determined by the charge-transfer controlled reduction of oxygen and the mixed charge- and mass-transfer controlled electrodissolution. In 0.1 M NaCl solution, three anodic regions are evidenced corresponding to: (I) a dissolution part from Eoc value, (II) a maximum current region corresponding to peaks formation and (III) a large current plateau. A partial protective effect of the corrosion product layer is observed at high anodic potential. It has been interpreted as the result of a 3D growth mechanism involving the formation of stable tin species in the layer according to a “pore resistance model”. Results on synthetic alloy are compared with those obtained on an archaeological bronze with a similar composition immersed in the same medium. Equivalent interface behaviour is evidenced between the synthetic and the archaeological bronzes.     

已锈蚀青铜在大气环境中的腐蚀发展及其保护研究

用动电位扫描法和循环伏安实验对青铜文物在模拟大气环境介质0.028 mol/L NaCl+0.01 mol/L Na2SO4+0.016 mol/L NaHCO3中的电化学行为进行了研究,探讨了CuCl、Cu2O、碱式氯化铜、混合锈对裸青铜的保护作用.结果表明：在腐蚀电位较负时,Cu2O、CuCl对基体有一定的保护性,而且保护性能优于碱式氯化铜和混合锈;在腐蚀电位较正时,Cu2O或CuCl对青铜的保护性变差,而此时碱式氯化铜和混合锈对裸青铜的保护性优于Cu2O、CuCl.0.1％MBO(2-巯基苯并恶唑)酒精溶液对裸青铜或被Cu2O、CuCl覆盖的青铜阳极过程有一定的抑制作用,对被碱式氯化铜或混合锈覆盖的青铜阳极过程有优异的抑制作用.       

含氢DLC膜的疏水性研究

目的：通过疏水性质的研究,证明源电极式和浸入式 PECVD 方法制备含氢 DLC 膜存在结构和性质上的差别,并且证明浸入式PECVD方法制备的含氢DLC膜更适于需要强疏水性的表面改性应用。方法在PECVD腔体中通入甲烷和氢气混合气体,同时在面对源电极的绝缘样品架上放置石英基片并沉积类聚合物DLC膜;在源电极上放置石英基片并沉积常规含氢DLC膜。在PECVD腔体中通入乙炔、氢气和四氟化碳混合气体,在面对源电极的绝缘样品架上放置石英基片并沉积掺氟 DLC 膜。改变气体压强和射频功率,生长一系列含氢DLC膜。利用紫外可见近红外光度计测试DLC膜的透射谱,扫描电子显微镜及原子力显微镜测试其表面形貌。利用接触角测量仪测试两种含氢DLC和一种掺氟DLC膜表面与水、甘油、乙二醇的接触角,并计算其表面能。比较两种含氢DLC膜接触角和表面能的差别,并根据类聚合物DLC膜的微观结构分析可能的原因。比较掺氟和不掺氟DLC膜的接触角并讨论比较结果。结果类聚合物DLC膜的接触角和表面能与具有相同光学带隙的常规含氢DLC膜存在明显差异。类聚合物DLC膜的接触角更大,表面能更低,因而具有更强的疏水性。类聚合物和常规含氢DLC膜与蒸馏水的接触角最大分别为91.2°和79.2°。类聚合物DLC膜中的碳原子具有更高的氢化率,可能是它表面能低和疏水性好的原因。掺氟DLC膜的接触角比具有相同带隙的类聚合物和常规含氢DLC膜都低,这与文献报道的掺氟能提高接触角的现象完全相反。结论类聚合物DLC膜的疏水性更强。结合其更小的内应力、更宽的光学带隙范围和更快的生长速度等特征,使它在医疗、光学保护涂层等领域具有更强的应用性。浸入式 PECVD 方法生长的掺氟 DLC 膜不但未提高反而降低了 DLC膜的疏水性,需要更多的研究来揭示其中的原因。     

古代青铜文物保护研究现状及AMT的应用

介绍了古代青铜文物腐蚀的主要产物、青铜病的起因 及危害,概述了国内外青铜文物保护现状,在作者前期研究结果基础上,总结了2-氨基-5- 巯基-1,3,4-噻二唑(AMT)作为青铜文物缓蚀保护剂的缓蚀性能和保护机制,指出了AMT用于青 铜文物保护的优势和未来的研究方向.     

Electrochemical and passive behaviour of Cu–Sn bronze in simulated archaeological soil media

The influence of formation potential on the electrochemical behaviour and passive film properties of Cu-28.6Sn bronze in simulated archaeological soil solutions was evaluated using combined potentiodynamic electrochemical measurements, electrochemical impedance spectroscopy, and the Mott–Schottky (MS) approach, with ex situ surface analytical techniques such as X-ray photoelectron spectroscopy. Passive films were formed in sodium chloride (NaCl) solution and a mixture of NaCl and sodium sulphate and their stability increased as the applied potential increased. The MS measurements indicated that a very thin p- and n-type porous passive film was formed on the bronze in the NaCl and sodium sulphate solution. The calculated donor density decreased exponentially with increasing passive film formation potentials in the NaCl solution and in the NaCl and sodium sulphate mixture. Based on the evaluations of the surface compositional analysis, the primary constituents of the films are Cu and Sn; in addition, dehydration of films was noted.     

Study of the corrosion behaviour of Cu-10Sn bronze in aerated Na2SO4 aqueous solution

Investigation of the electrochemical behaviour of Cu-10Sn (wt.%) alloy has been conducted in aerated aqueous sulphate solution and compared to that of pure Cu and Sn. Eoc versus time and cathodic and anodic polarizations have been performed as a function of the initial sulphate concentration, the rotation speed of the electrode and the immersion time. The surface layer have been characterized by scanning electron microscopy (SEM) and analyzed by energy dispersive spectrometry (EDS) and Fourier transform infrared spectroscopy (FTIR). The anodic behaviour evidences a Cu dissolution phenomenon on the corrosion layer limited by migration process rather than diffusion. The corrosion process conducts to preserve the original surface of the electrode and conducts to an internal growth at the layer/alloy interface, from the initial surface towards the unaltered substrate. The interphase behaviour is governed by the layer formed at Eoc under the experimental conditions and its evolution during the time. Hydroxyl-oxy and sulphate Cu and Sn compounds recover the surface and confer to the interface a blocking behaviour mainly due to the presence of the tin compounds in the layer. The global interphase behaviour matches the Type-I model of blocking adherent layer with decuprification phenomenon evidenced on archaeological bronzes.     

The atmospheric corrosion of quaternary bronzes: The leaching action of acid rain

The effect of leaching rain on the corrosion behaviour of bronze UNSC83600 was investigated as to the influence of alloying elements (Cu, Sn, Zn, Pb) through dropping tests simulating a severe runoff condition with a solution reproducing natural acid rain. Corrosion was followed with time monitoring both samples and leaching solutions (up to 30 days) by SEM, EDS, Raman spectroscopy, XRD, AAS. The bronze patina behaves as a porous layer enriched in stable tin compounds allowing uniform dissolution of Cu, Zn and partly of Pb. Laboratory results are in good agreement with field studies of outdoor bronzes in unsheltered condition.     

Investigation of high concentration of benzotriazole on corrosion behaviour of titania–benzotriazole hybrid nanostructured coating applied on Al 7075 by the sol–gel method

Nowadays, surface modification with self-healing ability is a valuable technique to improve chemical stability, oxidation behaviour and corrosion resistance of materials without interference with its physical, chemical or mechanical properties of bulk material underneath. In this paper, hybrid organic amorphous titania coatings are deposited on 7075 aluminium alloy substrates by using the sol–gel method. A titania–benzotriazole (BTA) nanostructured hybrid sol–gel coating is impregnated with three different high concentrations of BTA, 1.4, 2.8 and 4.2%. The bonds existing in the hybrid coating, structure and morphology and coating corrosion behaviour have been studied using the FTIR, GIXRD, field emission scanning electron microscopy and electrochemical impedance spectroscopy (EIS) test in a 3.5?wt-% NaCl solution during different immersion times, 24, 48, 72, 96 and 120?h. EIS studies indicated that a higher coating resistance value was gained for titania–4.2% BTA even after 120?h of immersion and BTA acted mainly on the amorphous titania coating as a corrosion inhibitor and a healing agent that acts by two mechanisms: first, release of a healing agent to the formation of corrosion products, then finally blocking surface defects; second, release of a healing agent during 48?h of immersion and its adsorption to produce an insulating layer on the surface of the coating in contact with the solution.     

Evaluation of the anticorrosive properties of benzotriazole alkyl derivatives on 6% Sn bronze alloy

This paper focuses on the anticorrosive behaviour of surface films formed by different benzotriazole alkyl derivatives on a Cu6Sn bronze (B6), whose composition is similar to materials used for outdoor artefacts. Some alkyl derivatives of the 1,2,3-benzotriazole (BTA) as: 5-hexyl-1,2,3-benzotriazole; 5-dodecyl-1,2,3-benzotriazole and [5-(1-undecyl)dodecyl]-1,2,3-benzotriazole were synthesized in order to investigate the influence exerted by the aliphatic chain on the inhibiting properties of the base molecule (BTA) toward bronze corrosion. The protective efficiency of the organic films, after a preliminary evaluation by electrochemical measurements, was determined by thin layer activation (TLA) and gravimetric techniques on the samples submitted to artificial weathering experiments in acid rain. For TLA measurements a γ-emitting radio nuclide ⁶⁵Zn (t_1/2 = 244 days), used as a corrosion tracer, was produced on the bronze surface by a high energy proton beam. At the end of artificial weathering exposures the radioactivity recovered on the bronze surface, once it was treated with a picking solution, allowed determination of the thickness loss. All the results arising from the different techniques, used in this study, show that BTA molecules bearing long aliphatic chain act as the best corrosion inhibitors.