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Mechanism of Corrosion
Published in Harry J. Meigh, Cast and Wrought Aluminium Bronzes, 2018
Fig. 8.3, known as an electro-chemical or galvanic series, shows the range of electrode potential values of a number of metals and alloys in natural sea water at 10°C (and also at 40°C in some cases). The electrode potential value is expressed in volts or millivolts relative to a Standard Calomel Electrode (SCE). It will be seen from Fig. 8.3 that most alloys experience a wide range of potentials in sea water, depending on conditions: water temperature, degree of aeration, turbulence of the water, pH value, biofouling, presence of chlorine etc. The potentially more severe corrosive condition of having two or more different metals immersed in the same electrolyte will be discussed below (see ‘Dissimilar metals – Galvanic coupling’).
Electrochemical Composition Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Michael J. Schöning, Arshak Poghossian, Olaf Glück, Marion Thust
The calomel electrode is the most common of all reference electrodes. It consists of a pool of mercury that is covered by a layer of mercurous chloride (calomel, Hg2Cl2). The calomel is in contact with a reference solution that is nearly always a solution of potassium chloride, saturated with mercurous chloride. Thus, the calomel electrode is a typical electrode of the second kind. Figure 55.6 shows a typical arrangement of a commercial calomel electrode assembly where the electrode is inverted, with the mercury uppermost, and packed into a narrow tube. Depending on the strength of the potassium chloride solution used, the electrode is called saturated calomel electrode (SCE), 3.8 or 3.5 M calomel electrode, respectively. Potassium chloride is used as reference solution because it gives rise to a small liquid junction potential at the outer liquid junction of the electrode, that is, the liquid junction with the sample. Hence, potassium chloride is a suitable reference solution as well as a good bridge solution. Furthermore, mercurous chloride has a very low solubility in potassium chloride solutions, regardless of concentration. The electrode reaction of a calomel electrode is
Effect of Ti on the corrosion behaviour of as-cast Fe–17Cr ferritic stainless steel
Published in Corrosion Engineering, Science and Technology, 2021
Junwei Fu, Kai Cui, Feng Li, Yucheng Wu
The solution used in the electrochemical tests was 10 wt-% HNO3 solution and 10 wt-% NaOH solution. Electrochemical tests were performed at room temperature using the electrochemical workstation using a three-electrode mode. The reference electrode is a saturated calomel electrode (SCE), the auxiliary electrode is a platinum electrode and the working electrode is the sample. In the experiments, potentiodynamic polarisation (PC) and electrochemical impedance spectroscopy (EIS) tests were performed. Before testing, the sample was immersed in the prepared solution for 1 h to obtain a stable open circuit potential (OCP). EIS tests were conducted after the OCP was stabilised. During EIS tests, the frequency ranged from 10−2 to 105 Hz, and the AC amplitude was 10 mV. For each frequency 12 data were measured. The obtained data from the EIS tests were fitted by Z-view2 software. The potentiodynamic polarisation tests in 10 wt-% NaOH solution and 10 wt-% HNO3 solution were carried out with the voltage range of −0.8 V (vs SCE) to 0.6 V (vs SCE) and −0.3 V (vs SCE) to 1.2 V (vs SCE), respectively. The scanning speed was 0.167 mV s−1, and each experiment was tested three times to ensure the repeatability.