Corrosion engineering | EPFL Graph Search

Corrosion engineering is an engineering specialty that applies scientific, technical, engineering skills, and knowledge of natural laws and physical resources to design and implement materials, structures, devices, systems, and procedures to manage corrosion. From a holistic perspective, corrosion is the phenomenon of metals returning to the state they are found in nature. The driving force that causes metals to corrode is a consequence of their temporary existence in metallic form. To produce metals starting from naturally occurring minerals and ores, it is necessary to provide a certain amount of energy, e.g. Iron ore in a blast furnace. It is therefore thermodynamically inevitable that these metals when exposed to various environments would revert to their state found in nature. Corrosion and corrosion engineering thus involves a study of chemical kinetics, thermodynamics, electrochemistry and materials science. Generally related to metallurgy or materials science, corrosion engineering also relates to non-metallics including ceramics, cement, composite material, and conductive materials such as carbon and graphite. Corrosion engineers often manage other not-strictly-corrosion processes including (but not restricted to) cracking, brittle fracture, crazing, fretting, erosion, and more typically categorized as Infrastructure asset management. In the 1990s, Imperial College London even offered a Master of Science degree entitled "The Corrosion of Engineering Materials". UMIST – University of Manchester Institute of Science and Technology and now part of the University of Manchester also offered a similar course. Corrosion Engineering master's degree courses are available worldwide and the curricula contain study material about the control and understanding of corrosion. Ohio State University has a corrosion center named after one of the more well known corrosion engineers Mars G Fontana. In the year 1995, it was reported that the costs of corrosion nationwide in the USA were nearly $300 billion per year.

Tribological and tribocorrosion behavior of nickel sliding against oxide ceramics

Stefano Mischler, Shoufan Cao, Junxiao Du

Nickel is widely used as a coating material in electroplating because of its good corrosion and wear resistance even at high temperature. Tribocorrosion has been identified as one of the main degradation mechanisms of nickel. This study evaluated the tribocorrosion behavior of pure nickel in citrate buffer solution (pH 4.5) under controlled mechanical, chemical and electrochemical conditions as well as wear of pure nickel in dry condition sliding against alumina or zirconia balls, respectively. The results showed that the wear of nickel was higher in passive domain due to wear accelerated corrosion compared to that in the cathodic domain. Surprisingly, both alumina and zirconia were worn by nickel in tribocorrosion condition under passive potentials as well as in dry condition. However, in the cathodic domain, negligible wear was observed on the alumina and zirconia balls. The formation of mixed nickel and aluminum/zirconium oxides was proposed as the wear mechanism of alumina and zirconia.

ELSEVIER SCIENCE SA2019

Corrosion Mechanisms of Diamond-like Carbon Coated Interlayers & Interfaces

Emilija Ilic

Diamond-like carbon (DLC) coatings can improve the wear resistance of articulating implants. However despite successful in-vitro testing, some DLC coated joint replacements had to be revised prematurely, mainly due to coating delamination induced by corrosion at the substrate/DLC interface. Body fluid will enter defective coating sites and if the reactively formed interface or interlayer materials are instable in the confined fluid, they with dissolve, resulting in delamination of the DLC and ultimate failure of the implant. The aim of this thesis is therefore to investigate the corrosion mechanisms responsible for delamination at a substrate/DLC interface in body-like media. This is achieved by developing and implementing experimental methodologies addressing/simulating aggravating factors such as confinements/crevices, galvanic coupling, stress and fatigue on the interface to investigate corrosion initiation, propagation, and failure. Firstly, corrosion initiation and galvanic coupling risk are addressed with a methodology for accessing and characterizing the reactivity of buried interlayers. The interlayer is revealed by ion beam polishing, forming a wedge-like profile of the substrate/interlayer/DLC. The composition and chemical state of the interlayer/interface is determined by Auger electron spectroscopy. Reactive interlayers/interfaces, Si, titanium (Ti) and chromium (Cr), formed new phases (carbides and oxides). These new materials are then characterized with a local-electrochemical microcapillary technique. Cr and Si-DLC based interlayers presented good passive behavior, while a Si interlayer corroded in bovine-based wear test fluid (HyClone® WTF). The influence of coating defects on the current response of DLC surfaces was also investigated by varying the exposed working area (cm2 to µm2 range). To address the failure case of a TiAlV/Si/DLC implant, the influence of confinements/crevices on corrosion propagation is investigated. It is shown that Si is highly vulnerable to corrosion in confined conditions. Pitting corrosion susceptibility is found in a crevice, whereas a Si dissolution rate of ca. 3.6 nm/h at 37 °C occurs within a confined area. The corrosion rates increased at elevated temperatures and yielded linear Arrhenius relations, with activation energies of 106 KJ/mol in phosphate buffered saline (PBS) and 109 KJ/mol in HyClone® WTF. Phosphorous species enhanced Si dissolution, while chlorides were not so influential. Galvanic coupling with Ti and applied stress further accelerated the Si dissolution. Finally, corrosion related fracture of a CoCrMo/DLC interface is investigated by applying static and cyclic load. A reciprocating sliding rig is utilized to determine the number of sliding cycles required for interface delamination to occur at a critical load, in PBS at 37 °C. The results followed a Wöhler curve relation. Small O2 contaminations (0.5 and 1.0%) at the interface adversely affected the CF behaviour by lowering the critical load and endurance limit. The fitted Wöhler curves could be extrapolated and were found to be in good agreement with long-term experimental results previously obtained on an implant in a spinal disk simulator.

EPFL2019

Capteur chimique à fibres optiques pour la mesure des ions chlore dans le béton à un stade précoce

Francine Laferrière

In the national and worldwide context, countless reinforced concrete structures are in an advanced state of deterioration. A principal cause of such degradation is chloride induced corrosion of reinforcement bars. This phenomenon is accentuated in countries where de-icing salts are used for road safety, as well as in maritime zones. To date, no non-destructive method reliably quantifies chloride content during the corrosion initiation phase. Measurement of such a parameter is important for development of a better understanding of the complexity of corrosion phenomena and more practically, for better management of existing structures. The principal objective of this study is to propose a method for non-destructive measurement in order to monitor continuously and in real time free chloride content in concrete pores. In this context, a chemical sensor that employs optical fibres was developed and tested. The sensor functions using the fluorescence of an indicator dye that is sensitive to chlorides. Through fluorescence spectroscopy, variations in the concentration of free chlorides are related to intensity fluctuations of fluorescence. In this type of sensor, the role reserved for optical fibres is limited to data transport, thereby enabling remote measurement. The use of optical fibres also provides an advantage compared with existing electric non-destructive detection systems due to superior electromagnetic stability. Theoretical and experimental studies calibrated and validated the sensor for implementation within mortar and concrete. Free chloride concentrations between 0 and 350 mM can be detected, this represents 0.05% and 0.6% of cement weight. The system stability is approximately 0.02% [Cl-]/year. Measurement accuracy is generally lower than ± 8%. Two experiments reproduced climatic variations in a controlled environment. The first test simulated a hot maritime climate and the second test simulated a cold continental climate. These tests confirmed that it is possible to determine with precision free chloride content. A constant temperature and relative humidity test showed a good concordance between results from the measurement system and an existing chloride transport model. Although measurements indicate faster chloride ingress compared with model predictions, test results and model predictions coincide after a few days. In conclusion, fluorescence spectroscopy with optical fibres offers an innovative means for early and non-destructive detection of free chloride content in concrete. Experiments and model predictions demonstrated complementary strengths and weaknesses. As a result, there is much potential for synergy in order to improve the science of corrosion process understanding and to plan appropriately for preventive action in practical situations.

EPFL2005