Gilded bronze conservation: assessment of protective treatments by accelerated ageing and of treatment removal procedures by laser cleaning

In the current study, we analyze the effectiveness of an organosilane compound, 3-mercapto-propyl-tri-methoxy-silane (abbreviated PropS-SH), in the corrosion protection of fire-gilded bronzes. Firstly, the coating was applied on as-gilded bronze. Subsequently, it was also applied on pre-patinated bronze, because the substrate on which protective coatings are applied in real conservation interventions are corroded artifacts (cleaning procedures never remove all the corrosion products). Aiming to obtain results that simulate the situation of real artifacts, a dropping test that simulates outdoor exposure in runoff conditions (unsheltered areas of monuments) was employed in order to prepatinate the gilded bronze samples, which are the substrate for applying the protective coating. The preparation of the samples by applying the protective coating was performed in collaboration with the Corrosion Studies Centre “Aldo Daccò” from Ferrara University. After the artificial exposure cycles the samples underwent investigations through a variety of spectroscopic methods including SEM, Raman, FIB, AAS and color measurements. In order to evaluate the possible removal of the organosilane coating, protected samples were subjected to laser cleaning tests and characterized by SEM/EDS so as to assess the changes in composition and morphology of the treated surfaces. The laser cleaning treatment was performed at the Institute of Applied Physics “Nello Carrara” (CNR Sesto Fiorentino (FI)). The morphology and chemical composition of the samples was observed before and after the operation in order to obtain information about the fluence and type of laser which are best suited to the removal of this type of coating.

The science of surface coatings.

Mode of access: Internet.

Considerations associated with the testing of external pipeline coatings

Reliable testing methodologies for the assessment of protective coatings are critical for ensuring the integrity and durability of pipeline coatings (such as field joint coatings) and the mitigation of pipeline corrosion. Currently the failure of joint coatings is one of the major concerns in corrosion protection of pipelines, although they represent only approximately 5% of the coated area in a pipeline system. This paper presents an overview of major testing methodologies currently used in the pipeline industry for the selection, testing, and life prediction of coatings, in particular field joint coatings. Particular focus is on the discussion of difficulties and limitations in testing methods for assessing pipeline coating cracking, cathodic disbondment and loss of adhesion. It is shown that there are limitations in current methodologies in evaluating the coating flexibility - a key parameter for avoiding coatings cracking during hydrostatic testing, cyclic pressure operation and field bending. Methodologies for assessing the effect of holidays in coatings on the cathodic disbondment of pipeline coating under excessively negative cathodic protection (CP) voltages also require improvement. Furthermore, methods for understanding the effects of coating wet adhesion on pipeline coating, cracking and disbondment also need attention. Some preliminary results for addressing some of these issues are also presented in this paper.

Fabrication of Electronic Materials from Australian Essential Oils

This RIRDC publication reports the findings and recommendations of the RIRDC funded study, "Fabrication of Electronic Materials from Australian Essential Oils". This project was undertaken to facilitate an expansion of the Australian Essential Oils Industry through the development of novel applications in the Electronic and Bio-Materials Industries. The findings presented in this report will provide value broadly across the Australian Essential Oils Industry, and more particularly to the growers involved in the production of tea tree, lavender and other essential oils. Several essential oils, namely tea tree oil, sandalwood oil, eucalyptus oil, alpha-pinene, d-limonene, lavender oil (a separate PhD project) and five major components of tea tree oil were tested. With the exception of sandalwood oil, all oils investigated were successfully polymerised. Importantly, this project determined that it is possible to use an environmentally friendly, inexpensive process of polymerisation to fabricate materials from essential oils in a reproducible manner with properties required by the optics, electronics, protective coatings, and bio-material industries.

Recent progress on synthesis, multi-scale structure, and properties of Y-Si-O oxides

Yttrium silicates (Y-Si-O oxides), including Y2Si2O7, Y2SiO5, and Y4·67(SiO4)3O apatite, have attracted wide attentions from material scientists and engineers, because of their extensive polymorphisms and important roles as grain boundary phases in improving the high-temperature mechanical/thermal properties of Si3N4and SiC ceramics. Recent interest in these materials has been renewed by their potential applications as high-temperature structural ceramics, oxidation protective coatings, and environmental barrier coatings (EBCs). The salient properties of Y-Si-O oxides are strongly related to their unique chemical bonds and microstructure features. An in-depth understanding on the synthesis - multi-scale structure-property relationships of the Y-Si-O oxides will shine a light on their performance and potential applications. In this review, recent progress of the synthesis, multi-scale structures, and properties of the Y-Si-O oxides are summarised. First, various methods for the synthesis of Y-Si-O ceramics in the forms of powders, bulks, and thin films/coatings are reviewed. Then, the crystal structures, chemical bonds, and atomic microstructures of the polymorphs in the Y-Si-O system are summarised. The third section focuses on the properties of Y-Si-O oxides, involving the mechanical, thermal, dielectric, and tribological properties, their environmental stability, and their structure-property relationships. The outlook for potential applications of Y-Si-O oxides is also highlighted.

Characterization of hydrophobin proteins at interfaces and in solutions using x rays

Hydrophobins are a group of particularly surface active proteins. The surface activity is demonstrated in the ready adsorption of hydrophobins to hydrophobic/hydrophilic interfaces such as the air/water interface. Adsorbed hydrophobins self-assemble into ordered films, lower the surface tension of water, and stabilize air bubbles and foams. Hydrophobin proteins originate from filamentous fungi. In the fungi the adsorbed hydrophobin films enable the growth of fungal aerial structures, form protective coatings and mediate the attachment of fungi to solid surfaces. This thesis focuses on hydrophobins HFBI, HFBII, and HFBIII from a rot fungus Trichoderma reesei. The self-assembled hydrophobin films were studied both at the air/water interface and on a solid substrate. In particular, using grazing-incidence x-ray diffraction and reflectivity, it was possible to characterize the hydrophobin films directly at the air/water interface. The in situ experiments yielded information on the arrangement of the protein molecules in the films. All the T. reesei hydrophobins were shown to self-assemble into highly crystalline, hexagonally ordered rafts. The thicknesses of these two-dimensional protein crystals were below 30 Å. Similar films were also obtained on silicon substrates. The adsorption of the proteins is likely to be driven by the hydrophobic effect, but the self-assembly into ordered films involves also specific protein-protein interactions. The protein-protein interactions lead to differences in the arrangement of the molecules in the HFBI, HFBII, and HFBIII protein films, as seen in the grazing-incidence x-ray diffraction data. The protein-protein interactions were further probed in solution using small-angle x-ray scattering. Both HFBI and HFBII were shown to form mainly tetramers in aqueous solution. By modifying the solution conditions and thereby the interactions, it was shown that the association was due to the hydrophobic effect. The stable tetrameric assemblies could tolerate heating and changes in pH. The stability of the structure facilitates the persistence of these secreted proteins in the soil.

Quantitative approaches for characterising fibrillar protein nanostructures

Polypeptide sequences have an inherent tendency to self-assemble into filamentous nanostructures commonly known as amyloid fibrils. Such self-assembly is used in nature to generate a variety of functional materials ranging from protective coatings in bacteria to catalytic scaffolds in mammals. The aberrant self-assembly of misfolded peptides and proteins is also, however, implicated in a range of disease states including neurodegenerative conditions such as Alzheimer's and Parkinson's diseases. It is increasingly evident that the intrinsic material properties of these structures are crucial for understanding the thermodynamics and kinetics of the pathological deposition of proteins, particularly as the mechanical fragmentation of aggregates enhances the rate of protein deposition by exposing new fibril ends which can promote further growth. We discuss here recent advances in physical techniques that are able to characterise the hierarchical self-assembly of misfolded protein molecnles and define their properties. © 2010 Materials Research Society.

The study on the interface adhesion comparison of the MgF2, Al2O3, SiO2 and Ag thin films

Adhesion between the interface of pure silver thin film and three kinds of low refractive index coatings MgF2, Al2O3, SiO2 were compared in this article. The results indicated that the adhesion of Al2O3 and Ag was evidently superior to that of MgF2 and Ag, and the adhesion of MgF2 and Ag was evidently superior to that Of SiO2 and Ag. Reasons were analyzed accordingly. On the other hand, we compared the effect on the optical characteristic of Ag film when these three kinds of films were used as protective coatings and enhanced coatings. Considering the difference of the adhesion between Ag and MgF2, Al2O3, SiO2, suited uses are given for each other. © 2004 Elsevier B.V. All rights reserved.

Electroless nickel composite (Ni-P/SiC) coating - A study on interface and corrosion characteristic

Surface behaviour is of paramount importance as failure and degradation tend to initiate from the surface. Electroless composite coating (NiP/SiC) was developed using SiC as reinforcing particles. As heat treatment plays a vital role in electroless nickel coating owing to the changes in microstructure, phase structure and mechanical properties, an insight at the interface changes in chemistry and micromechanical behaviour was investigated using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) and microindentation techniques. Corrosion performance was analysed using electrochemical impedance spectroscopy (EIS). Absence of zinc and migration of copper at the interface was detected. Brittleness and microcracks was seen long the interface when indenting at load of 500 gf (Vickers). Corrosion performance is weaker than particles free coating. However, a thin blanket of NiP could enhance the resistance to corrosive medium.

An investigation on the preparation and properties of some transparent conducting oxides and lead selenide thin films”

The investigation of physical properties of matter has progressed so much during the last hundred years. Today physics is divided in to a large distinct group of special branches. These branches are distinguished by the particular area studied, method of investigation and so on. An independent and important branch that has developed is the physics ofthin films.Any object in solid or liquid form with one of its dimensions very much smaller than that of the other two may be called a thin film. It is having only one common property, namely, one of their dimensions is very small, though all their physical properties may be different. Thin layers of oil, floating on the surface of water, with their fascinating colours, have attracted men’s curiosity from time immemorial. The earliest application of thin films was the protective coatings in the form of paints. A thin layer of tin has been used from ancient times to protect copper utensils from corrosion. Indium thin films are used in certain applications on account of their good lubricating property. Relay contacts are coated with thin films of rare earth metals in order to prevent burning due to arcing. Hard coatings are also available using diamond like carbon (i-carbon). The basic properties of thin films are of considerable interest because of their potential applications in various fields of science and technology

Electrochemical Behaviour of the AA2024 Aluminium Alloy Modified with Self-Assembled Monolayers/Polyaniline Double Films

The electrochemical characteristics of the AA2024 aluminium alloy modified with octadecyltrimethoxysilane (ODTMS) + polyaniline (PANi) and propiltrimethoxysilane (PTMS) + (PANi) were studied in the present work. The results show that the different protective coatings shift the values of corrosion and pit potentials to more positive values making the system nobler and indicate that the double film ODTMS + PANi present the best protection against corrosion characteristics, that is probably due to the two contributions: anodic protection associated with the barrier effect.

An overview of methods for simulating and evaluating pipeline corrosion

Steel pipelines, buried under the soil and protected by the combination of protective coatings and cathodic protection (CP), are used for oil and gas transportation. These pipelines are one of the critical infrastructures for energy transportation and therefore became lifelines of modern society. The deterioration of the external surfaces of transmission pipelines is a serious problem and is caused mainly by coating and/or CP failure leading to the loss of integrity of pipelines. To avoid such damage, there is a need of techniques which are able to locate active corrosion sites, monitor corrosion, and evaluate corrosion damage. Fundamental understanding of such processes occurring on coated pipelines (with various types of defects in coatings as well as pipe) in complex soil environment is necessary for the development of such techniques. Numerous laboratory techniques, i.e., electrochemical impedance spectroscopy based, polarisation measurements based, mathematical simulations, direct observation etc. have been used to develop fundamental understanding, simulate and evaluate corrosion occurring in oil and gas pipelines under various operating conditions. Given the complex nature of the pipeline corrosion, application of these laboratory techniques in field measurements as well as in understanding the corrosion mechanisms is lacking. This paper presents an overview of investigations, based on electrochemical techniques, for simulation and evaluation of pipeline corrosion in laboratory.

An overview of new progresses in understanding pipeline corrosion

An approach to achieving the ambitious goal of cost effectively extending the safe operation life of energy pipeline to 100 years is the application of health monitoring and life prediction tools that are able to provide both long-term remnant pipeline life prediction and in-situ pipeline condition monitoring. A critical step is the enhancement of technological capabilities that are required for understanding and quantifying the effects of key factors influencing buried steel pipeline corrosion and environmentally assisted materials degradation, and the development of condition monitoring technologies that are able to provide in-situ monitoring and site-specific warning of pipeline damage. This paper provides an overview of our current research aimed at developing new sensors and electrochemical cells for monitoring, categorising and quantifying the level and nature of external pipeline and coating damages under the combined effects of various inter-related variables and processes such as localised corrosion, coating cracking and disbondment, cathodic shielding, transit loss of cathodic protection.

Influence of anodization on the fatigue strength of 7050-T7451 aluminium alloy

In recent years, with higher demand for improved quality and corrosion resistance, recovered substrates have been extensively used. Consequently residual stresses originated from these coatings reduce the fatigue strength of a component. Due to this negative influence occasioned by corrosion resistance protective coatings, an effective process like shot peening must be considered to improve the fatigue strength. The shot peening treatment pushes the crack sources beneath the surface in most of medium and high cycle cases due to the compressive residual stress field (CRSF) induced. The aim of this study was to evaluate the influence on the fatigue life of anodic films grown on 7050-T7451 aluminium alloy by sulphuric acid anodizing, chromic acid anodizing and hard anodizing. The influence on the rotating and reverse bending fatigue strength of anodic films grown on the aluminium alloy is to degrade the stress life fatigue performance of the base material.A consistent gain in fatigue life in relation to the base material was obtained through the shot peening process in coated specimens, associated to a residual stress field compressive near the surface, useful to avoid fatigue crack nucleation and delay or even stop crack propagation.