Search results for "CORROSION"
showing 10 items of 456 documents
Fatigue crack growth behaviour of four structural steels in air and in a geothermal fluid environment
1992
Abstract In recent years the exploitation of geothermal energy has expanded rapidly in Italy. This has created a requirement for improved drilling technology, to reduce the number of failures occuring in the drills, which is more frequent than in oil wells. This paper deals with the results obtained in FCCR tests of four materials both in air and in two types of aggressive environments. Deterioration takes place by fatigue, corrosion fatigue and hydrogen embrittlement. It is concluded that the steel G105 is a suitable substitute for S135 in drill pipes, and inspections between drillings may be adequate to prevent failure for small-curvature wells.
Guided Wave Propagation in a Plate Edge and Application to NDI of Rail Base
2012
The analysis of guided wave propagation in a plate edge can be useful for some applications, such as for the inspection of the rail base. Here guided waves generated by a laser beam hitting, on the inclined surface, a solid media with trapezoidal cross-section have been studied. We have found that, for the geometry investigated, two guided waves propagate along both free surfaces of the plate, with same velocity and frequency. The analysis of the trajectories of the two material points, due to waves propagation, shows that the wave packets can be identified as Rayleigh waves. The presence of S0 Lamb mode, with low frequency and low amplitude, has been revealed too. As an example of a possib…
Failure by corrosion in PC bridges: A case history of a viaduct in Italy
2016
Purpose The paper illustrates a viaduct collapse due to corrosion phenomena. Moreover, a contribution to the issues related to both the control of existing structures and design methods to be followed for the construction of new buildings is provided. Design/methodology/approach The objectives were achieved by in situ observations and numerical analyses. The effects of corrosion phenomena are investigated, and the progressive collapse analysis is provided to be helpful in this case. Findings The damages induced by corrosion phenomena have caused the collapse of the viaduct taken in to account. The performed numerical analyses were able to reproduce the effects of corrosion in terms of redu…
Effects of corrosion on a steel bowstring bridge in marine environment: A case-study of assessment and retrofit
2021
The case-study of a steel bowstring bridge set in a marine environment and highly damaged by corrosion is presented. The bridge was built in 2004 and was repainted for corrosion protection in 2010. Despite the recent construction and the maintenance interventions, many structural elements like hangers are highly damaged by corrosion with decreasing performance in terms of serviceability and ultimate limit states. A deep investigation was carried out in order to assess the bridge and to establish the necessary retrofit actions to be carried out in the near future. In-situ tests reveal the reduced performance of the original steel in terms of strength and corrosion protection, together with t…
Insight on bacteria communities in outdoor bronze and marble artefacts in a changing environment
2022
Epilithic bacteria play a fundamental role in the conservation of cultural heritage (CH) materials. On stones, bacterial communities cause both degradation and bioprotection actions. Bronze biocorrosion in non-burial conditions is rarely studied. Only few studies have examined the relationship between bacteria communities and the chemical composi- tion of patinas (surface degradation layers). A better comprehension of bacterial communities growing on our CH is fundamental not only to understand the related decay mechanisms but also to foresee possible shifts in their compo- sition due to climate change. The present study aims at (1) characterizing bacterial communities on bronze andmarble s…
Comparison of organic peracids in wastewater treatment: Disinfection, oxidation and corrosion.
2015
The use of organic peracids in wastewater treatment is attracting increasing interest. The common beneficial features of peracids are effective anti-microbial properties, lack of harmful disinfection by-products and high oxidation power. In this study performic (PFA), peracetic (PAA) and perpropionic acids (PPA) were synthesized and compared in laboratory batch experiments for the inactivation of Escherichia coli and enterococci in tertiary wastewater, oxidation of bisphenol-A and for corrosive properties. Disinfection tests revealed PFA to be a more potent disinfectant than PAA or PPA. 1.5 mg L(-1) dose and 2 min of contact time already resulted in 3.0 log E. coli and 1.2 log enterococci r…
Study of nickel corrosion processes by molecular dynamics with reactive potential ReaxFF
2012
Understanding of corrosion processes is important for the study of the durability of materials in aggressive environment. The objective is to provide new lights on the corrosion processes of nickel in aqueous condition with molecular dynamics simulation using a reactive force field "ReaxFF."We are particularly interested by the reaction between water molecules and mono-crystalline surfaces of nickel. No dissociation of water was showed on the surfaces. Moreover, an adsorption of molecules in bilayer was observed, reflecting the mutual polarization between water and nickel, which confirms the charge calculation. The metal surface is positively charged and the first water layer charged negati…
Mechanism of brittle fracture in a ductile 316 alloy during stress corrosion
1990
Abstract The ductile f.c.c. 316 alloy is shown to exhibit brittle transgranular (and intergranular) stress corrosion cracking in a 153°C MgCl2 solution at free corrosion potential. Tests on smooth and pre-cracked specimens are performed to identify the mechanisms of fracture. Transgranular cracking is related to both a discontinuous microcleavage mainly on {100} planes and a microshearing on {111} planes. A new physical modelization is proposed to explain the brittle transgranular cracking. It is based on the influence of the localized anodic dissolution on the enhancement of the plasticity at the crack tip. The formation of dislocation pile-ups and the conditions of restricted slip induce …
Tools for studying water vapor at high temperatures
2014
1. Kinetics and Oxidation Mechanisms 1.1 Experimental Devices that Produce Water Vapor1.2 Using the Jump Method to Understand Oxidation Mechanisms and Kinetics1.3 Detection of Breakaway Oxidation with Acoustic Emission during Thermal Oxide Scale Growth 1.4 Stress Analysis during and after Oxidation 2. Characterization 2.1 Use and Potential of Environmental SEM (ESEM) in High-Temperature Oxidation and Corrosion Studies in Wet Air 2.2 In Situ X-Ray Diffraction for Water Vapor Analyses2.3 Use of Synchrotron Beam for Evaluating the Influence of Water Vapor on the Corrosion of Metallic Materials 2.4 Raman Spectrometry2.5 In Situ Steam Oxidation Chamber Coupled to XPS 2.6 Hydrogen Profiling in Ox…
3 Probing and Modelling of Galvanic Coupling Phenomena in Localized Corrosion
2011
The basic driving force of localized corrosion or corrosion protection in numerous cases is the galvanic coupling of which the dimensional aspect is fixed by a combination of scales regarding interfacial processes or properties. At the electrolyte–metal interface, it is necessary to consider the microstructure (including all real-time modification induced for example by applied stresses), the possible chemical changes at the surface of the material, and the electrolyte conductivity contribution, among others factors.