China
Africa
Explore chapters and articles related to this topic
Imperfections and Diffusion
Published in Yip-Wah Chung, Monica Kapoor, Introduction to Materials Science and Engineering, 2022
Another type of planar defects is the external surface of a material. Surface atoms, because of their unique environment, have fewer nearest neighbors. Consequently, a surface is thermodynamically unstable and is chemically more reactive than the bulk. Surface atoms, when given enough mobility, will attempt to obtain maximum coordination and hence lower surface-free energy. The action of catalysts (used widely in the petroleum industry and automobile catalytic converters) relies on these properties of surface atoms. Corrosion is an electrochemical process that occurs on surfaces due to heterogeneities in electrochemical potentials. Examples of other planar defects include stacking faults (i.e., departure from the normal stacking sequence of atoms), boundaries between phases (e.g., interface between the almost pure iron matrix in steel and iron carbide precipitate), and boundaries between ferromagnetic domains.
Smart Bridge: The duraBASt test bridge equipped with RFID-based sensors
Published in Hiroshi Yokota, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations, 2021
C. Strangfeld, I. Hindersmann, E. Niederleithinger
Mainly two issues (among others) are responsible for the occurrence of active chloride induced corrosion (Nürnberger 1995). When a certain minimum moisture level is given, anode and cathode are coupled into this electrolytic system. Then, the oxidation of iron ions induces a shift of the electrochemical potential at the rebar. The onset of corrosion with low corrosion rates already generates a significant change of the electrochemical potential. For this reason, moisture and corrosion sensors have been developed and were installed in the duraBASt bridge. The wireless sensors work with radio frequency identification (RFID) and are embedded completely in concrete. Thus, the concrete cover remains intact. The RFID based sensors are passive and robust and are able to record data for several decades. They detect corrosion already at its initial state. The sensor data enables a robust and reliable way of monitoring the building condition with regard to moisture and corrosion. This approach may contribute to an efficient and cost reducing maintenance of our infrastructure.
Effect of Bi content on microstructure and corrosion behaviour of Zn–8Al–(Bi) alloys
Published in Corrosion Engineering, Science and Technology, 2021
Rudimylla Septimio, Maria A. Arenas, Ana Conde, Iñaki Garcia, Amauri Garcia, Noé Cheung, Juan de Damborenea
Several investigations have reported that the microstructure plays an important role on mechanical properties, wear resistance and corrosion behaviour of metallic alloys, highlighting the importance of microstructural control through solidification thermal parameters during the casting process [25–38]. In addition, the elements that constitute the alloy affect its corrosion behaviour [39]. Due to the electrochemical potential of each metallic element an active corrosion cell that accelerates the alloy degradation can be formed. In this sense, caution must be taken when adding alloying elements, particles or reinforcing fibres aiming to improve the mechanical and wear properties of metallic alloys. They can cause accelerated corrosion of the metallic matrix by inducing the formation of galvanic couples. When it is not possible to seek maximisation of all properties by adding a third element, it is necessary to search for a balance among the properties that satisfy the needs imposed by the project component [40].
On the Volta potential measured by SKPFM – fundamental and practical aspects with relevance to corrosion science
Published in Corrosion Engineering, Science and Technology, 2019
Cem Örnek, Christofer Leygraf, Jinshan Pan
The discussion so far does not involve any effect of the electrolyte. For a metal in an electrolyte, the situation is more complicated. The electrochemical potential of an electrode in an electrolyte depends on the structure of the electrochemical double layer at the electrode/electrolyte interface and the electrochemical reaction(s) taking place on the electrode surface. According to Trasatti’s notation, the electrochemical electrode potential includes the Volta potential and the Volta potential difference at the electrode/electrolyte interface so that the interfacial parameters also have an influence on the electrode potential [45]. A similar concept was seen also in earlier communication by Rüetschi and Delahay [30]. Moreover, the corrosion potential of a metal in an electrolyte is a mixed potential reached at the open-circuit condition, which depends on the coupled anodic and cathodic reactions (mixed-potential theory), and also on other parameters such as the surface film formed as well as the Ohmic resistance of the electrolyte. These factors should be kept in mind when correlating the measured Volta potential with the corrosion potential [46].
Corrosion and tribocorrosion study of 316L steel, Ti–6Al–4V and Ti–10Zr–10Nb–5Ta
Published in Tribology - Materials, Surfaces & Interfaces, 2019
S. Carquigny, J. Takadoum, S. Ivanescu
Proteins can also influence greatly wear resistance of metal surface in aqueous solution by adsorbing and forming a lubricating protective biofilm [6,16]. When materials are submitted to corrosion and wear (tribocorrosion), as in the case for numerous implanted biomaterials, complex mechano-electrochemical reactions and interactions occur between the rubbing surfaces and the aqueous environment. The synergistic effect between corrosion and wear may lead to an important material removal whose extent depends on several factors: chemical composition of the electrolytes, chemical composition and mechanical properties of the materials, surface energy, topography, hydrophilic or hydrophobic properties, applied electrochemical potential (open circuit potential, cathodic or anodic applied potential), wear tests conditions. In [14] the authors have studied the effect of proteins on corrosion rates of 316L stainless steel, pure titanium and Ti–6Al–4V alloy in static and freeting modes. They found that, in static mode, proteins increased the corrosion rate of stainless steel and titanium but did not have any effect on Ti–6Al–4V alloy. Conversely, in the fretting mode proteins decreased the corrosion rate of the stainless steel but did not have any significant effect on the other materials. The obtained results reported above, concerning Ti–6Al–4V, has been confirmed in another freeting study [17] where the authors reported that proteins do affect neither the wear rate nor friction nor wear-accelerated corrosion of the material. Similar results have been reported elsewhere [18,19].