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Precast segmental bridge construction in seismic zones
Published in Fabio Biondini, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Resilience and Sustainability, 2012
Fabio Biondini, Dan M. Frangopol
Concrete can be cathodically protected using various methods by means of either an impressed current (ICCP) or galvanic (sacrificial) system. Both systems work by polarising the reinforcement in an electrical circuit so the anodic, dissolution mechanism is forced to take place at an installed anode. ICCP systems generally use inert long-life electrodes such as mixed metal oxide coated titanium or titania ceramic. The reinforcement is polarised using an external DC power source. Galvanic systems use less noble metal electrodes, commonly zinc, aluminium or magnesium, which corrode preferentially to the steel and thereby generate the required protection. CP has also an additional beneficial effect in that negatively charged chloride ions are repelled from the steel towards the anode, enhancing corrosion protection. The main benefit for the structure is that it is not necessary to remove all of the chloride- contaminated concrete. This is beneficial not only because it reduces the volume of concrete removed but also because it often eliminates the need to support the structure during the work (Lambert 1998).
Physical Properties of Metals
Published in Vladimir B. Ginzburg, Steel-Rolling Technology, 1989
Two types of corrosion processes are known [3,9]:Electrochemical corrosion - It occurs when a current flows between cathodic and anodic areas on metallic surfaces.Galvanic corrosion - It is associated with electric current produced by a galvanic cell consisting of two different conductors in an electrolyte or two similar conductors in different electrolytes. in case of two different steels (bimetal), the resulting reaction, or 'couple action', is regulated by: a) the metal to which the steel is coupled, b) the conductivity of the solution in which it is service, c) the contact area between metals, and d) presence or absence of oxygen or other depolarizing agents.
Recycling of Metalworking Fluids
Published in Jerry P. Byers, Metalworking Fluids, Third Edition, 2018
Galvanic reactions occur when one metal corrodes preferentially versus another when both metals are in electrical contact, such as in the presence of an electrolyte (metalworking fluid). The electron reaction induces negative charges into the fluid, which can destabilize metalworking fluids.
Effect of hydrostatic pressure on galvanic corrosion of low-alloy steel in simulated deep-sea environments
Published in Corrosion Engineering, Science and Technology, 2022
Yuxin Wang, Fulei Yan, Bo Wu, Jianhua Wu, Kefeng Hu, Xianbin Hou, Leyang Dai
The increase in hydrostatic pressure causes the corrosion potential of the three low-alloy steels to shift negatively, thus facilitating the conversion process of the intermediate product γ-FeOOH to , accelerating the process of cathodic reaction, and the generated can be used as a large cathode to accelerate corrosion. The increase in hydrostatic pressure will also change the morphology of corrosion products. The corrosion products under high pressure are more likely to form crack defects, making it easier for corrosion ions to contact the substrate surface and accelerate corrosion.Although the potential difference between the three low-alloy steels is slight (<60 mV), severe galvanic corrosion still occurs after coupling. Under different hydrostatic pressure conditions, 907A is used as the anode of the 907A/921A1# system, and the protection current is output to the 921A steel and 1# steel (cathodes), and the corrosion is aggravated., while 921A steel and 1# steel are used as cathodes, corrosion will slow down. Therefore, in engineering applications, the galvanic corrosion of metals with low potential differences cannot be ignored, and coatings and cathodic protection must be used for total protection.
Galvanic corrosion of aluminium alloy members of bridge guiderails under severe atmospheric exposure conditions
Published in Corrosion Engineering, Science and Technology, 2019
Emmanuel Mrema, Yoshito Itoh, Akira Kaneko
Aluminium alloy guiderails are commonly used on bridges constructed in marine environments due to the proven durability of aluminium alloy materials. However, to ensure a higher structural strength at key points, the fasteners in these aluminium alloy structures continue to be made of steel. The contact between the aluminium alloy and the steel fasteners can trigger galvanic corrosion in the aluminium alloy under severe atmospheric conditions [2]. Galvanic corrosion is an electrochemical deterioration of a metal occurring when two dissimilar metals (electrodes) with a potential difference between them come in contact in an electrolytic environment. For galvanic corrosion to occur, three conditions have to be met: the metals must be far apart in the galvanic series, they must be in an electrolytic environment and they must be electrically in contact [5]. Normally, the more anodic metal dissolves in the electrolyte and the dissolved particles migrate to the more cathodic metal. In this sense, the more anodic metal is considered to have undergone galvanic corrosion. The severity of the corrosion increases with the increase of the area in contact with the cathodic metal [6]. One of the most common triggers of galvanic corrosion is a combination of stainless or mild steel fasteners with aluminium alloy members, as illustrated in Figure 1. Galvanic corrosion can be inhibited by preventing the electric flow between the two dissimilar metals through proper insulation or through some appropriate surface treatment on either metal.
Galvanic corrosion analysis of a Bi–Zn solder alloy coupled to Ni and Cu substrates
Published in Corrosion Engineering, Science and Technology, 2020
Rudimylla S. Septimio, Maria A. Arenas, Ana Conde, Amauri Garcia, Noé Cheung, Juan de Damborenea
Galvanic corrosion, also known as ‘dissimilar metal corrosion’, occurs when two (or more) dissimilar metals are electrically coupled under the presence of an electrolyte. In this context, the noblest metal will act as a cathode leading the less noble metal to degrade; in other words, it increases the corrosion of the anode. Galvanic corrosion has been one of the major concerns for industry since the modern engineering structures are commonly created by joining dissimilar materials [1,2]. This kind of corrosion is very common in aircraft [3–7], petroleum [8–10], civil engineering and architecture [11,12] and shipping industries [13,14], resulting a great economic and safety burden [2].