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Types of Corrosion in the Offshore Environment
Published in Karan Sotoodeh, Coating Application for Piping, Valves and Actuators in Offshore Oil and Gas Industry, 2023
Corrosion occurs because of the formation of electrochemical cells. An electrochemical cell is defined as a device capable of either deriving electrical energy from chemical reactions or facilitating a chemical reaction by introducing electrical energy. A common type of electrochemical cell is a battery, also known as a galvanic cell, in which electrical electricity is produced from a chemical reaction. An electrochemical corrosion cell includes four necessary factors. In other words, corrosion requires four elements to occur. These are listed below; if one of the elements or factors is eliminated, corrosion will not occur.
Electrochemistry
Published in W. John Rankin, Chemical Thermodynamics, 2019
The voltage of an electrochemical cell is the potential difference between the electrodes of each of the half-cells. The potential of a half-cell cannot be measured absolutely, but it can be measured relative to a reference half-cell. For aqueous electrolyte solutions the reference half-cell is the standard hydrogen electrode (SHE),Pt(s)|H2(g,p=1bar)|H+(aq,a=1)
Corrosion Studies
Published in P.J. Gellings, H.J.M. Bouwmeester, Electrochemistry, 2019
An electrochemical cell consists of two electrodes (anode and cathode) and an electrolyte. For studies of the formation of oxide product layers on metals at high temperatures it can be very useful to describe the reaction system Metal/Oxide/Gas as an electrochemical cell. In this special case the anode is formed by the metal to be oxidized, the cathode by an oxygen electrode, and the electrolyte by the oxide product layer, as shown in Figure 15.3. It is a special case of the galvanic cell normally used to describe a corrosion cell. However, in this all-solid state corrosion cell, electronic charge transport takes place through the same phase as the ionic charge transport. The metal oxide product layer serves as the electrolyte while during growth of the oxide layer electrons are also transported to the oxygen cathode, or for a p-type semiconductor holes in the opposite direction, as described in Section II.
The role of microstructure modifications on electrochemical and plasma-nitriding behaviour of 316L steel produced by laser powder bed fusion
Published in Philosophical Magazine, 2023
Vikesh Kumar, Catalin Iulian Pruncu, Yaping Wang, Carlos A. Figueroa, Indrasen Singh, Santosh S. Hosmani
The linear polarisation results (see Figure 6(c) and (d)) demonstrate a correlation between electrode potential and current generated in an electrochemical cell for a specific material. Excellent agreement between the OCP and linear polarisation behaviour is seen in Figure 6. Table 2 displays the corrosion parameters obtained from fitting the Tafel plots. Typically, a relatively higher value of Ecorr indicates higher corrosion resistance, while a higher value of Icorr indicates a higher corrosion rate (i.e. lower protection against corrosion). Therefore, high Ecorr and low Icorr values indicate excellent corrosion properties. Figure 6(c) indicates the maximum and minimum Icorr for the HNS (1.19 µA.cm−2) and VNS (0.621 µA.cm−2) samples, respectively. Moreover, the Ecorr value of the VNS is more positive (−258.17 mV) than the HNS sample (−306.44 mV). A further reduction in Icorr and an increase in Ecorr are observed after severe surface deformation (see Figure 6(d) and Table 2).
Impact of gas film thickness on the performance of RM-ECDM process during machining of glass
Published in Materials and Manufacturing Processes, 2022
Tarlochan Singh, Akshay Dvivedi
Electrolyte provides the conductive path to move the ions to pass the current across the electrochemical cell circuit. The rise in concentration of NaOH electrolyte increases the ions movement in the electrolytic bath. Thus, it results in fast electrochemical reactions. In the ECDM process, this faster reaction rate contributes to decide the film formation characteristics and subsequent EC Discharges and energy at the machining vicinity. As illustrated in Fig. 5, the film thickness surges with a rise in the electrolyte concentration. On the other side, this incremental change in film formation results in high aspect ratio holes forming by liberating the high thermal energy. The material removal rate also increases. However, beyond 21%, the sharp increase in film thickness decreases the MRR and L/D ratio. The reason for this is the stray discharges accomplished owing to the gathering of bubbles at the hole entrance. It can be inferred that the energy generated from the 21% electrolyte concentration is sufficient to make appropriate synchronization with the additionally augmented rotary tool motion. Beyond this value, the tool rpm’s should be high in direction to form stable film. The increase in the concentration of hydroxyl ions with an increase in the concentration could be another reason to promote the chemical etching phenomenon, which may be further used to increase the hole’s diameter and results in the low aspect ratio.
A virtuous cycle in materials engineering and surface finishing: design-print-image
Published in Transactions of the IMF, 2020
F. C. Walsh, L. F. Arenas, C. Ponce de León
Electrochemical cells continue to find use in the synthesis and processing of selected commodity and fine chemicals both in the research laboratory and in industry.1–6 One of the challenges facing the technology is the increasing need to achieve a high performance from cells which are easily designed, manufactured or modified. This is particularly true of flow cells1,2 used in energy conversion and storage, such as redox flow batteries,7,8 electrosynthesis of organics,9–11 environmental remediation (including removal of metals12,13 and organic contaminants14,15 from process streams and wastewaters), specialised electrodeposition of metals16–18 and composite coatings19 as well as electrochemical machining.20