Abstract:Metals and alloys such as aluminum (Al), stainless steels, and nickel-based alloys exhibit corrosion resistance in a wide range of environments due to the presence of protective, passive oxides. However, in environments that contain aggressive anions such as chloride, Cl − , the passive film becomes unstable and degrades locally causing film breakdown and pitting corrosion. A number of theories describing the initiation of pitting corrosion have been postulated and discussed but to date there is no consensus o… Show more
“…These super-Faradaic efficiencies are reported in the literature and they may be explained in terms of chemical dissolution of the anode (4), chemical attack of both anode and cathode, which can occur due to acidity and alkalinity produced in the vicinity of the electrodes (31) and pitting corrosion of the anode, caused by chloride ions (32). Figure 6 shows the amount of dissolved aluminum when an aluminum plate was dipped into a NaCl solution for 24 h. One can observe that as the chloride concentration increases, the amount of dissolved aluminum is higher, which is consistent to the literature data that says that the higher the chloride concentration, the higher is the corrosion promoted by Cl-ions over aluminum surface (33)(34)(35)(36)(37)(38)(39). It is also possible to notice that the amount of chemically dissolved aluminum is small.…”
Borsa, MB.; Jungblut, R.; Pérez-Herranz, V.; Müller, L.; Moura Bernardes, A.; Bergmann, C. (2016). Electrochemical treatment of a graphitic forging lubricant effluent: The effect of chloride concentration and current density. Separation Science and Technology. 51 (1)
ABSTRACTThe graphite removal and the chemical oxygen demand (COD) reduction by the electrochemical treatment of an effluent containing a lubricant (oil in water emulsion with graphite) was investigated. The electrochemical cell used a pair of aluminum plates.Since the effluent conductivity was very low, NaCl was used as supporting electrolyte and different current densities as well as different distance between the electrodes were applied. In lower current densities, higher chloride concentrations implied in smaller COD values. The same behavior was observed when electrode distance was decreased. All the tested conditions presented significant graphite removal and COD reductions larger than 94%.
“…These super-Faradaic efficiencies are reported in the literature and they may be explained in terms of chemical dissolution of the anode (4), chemical attack of both anode and cathode, which can occur due to acidity and alkalinity produced in the vicinity of the electrodes (31) and pitting corrosion of the anode, caused by chloride ions (32). Figure 6 shows the amount of dissolved aluminum when an aluminum plate was dipped into a NaCl solution for 24 h. One can observe that as the chloride concentration increases, the amount of dissolved aluminum is higher, which is consistent to the literature data that says that the higher the chloride concentration, the higher is the corrosion promoted by Cl-ions over aluminum surface (33)(34)(35)(36)(37)(38)(39). It is also possible to notice that the amount of chemically dissolved aluminum is small.…”
Borsa, MB.; Jungblut, R.; Pérez-Herranz, V.; Müller, L.; Moura Bernardes, A.; Bergmann, C. (2016). Electrochemical treatment of a graphitic forging lubricant effluent: The effect of chloride concentration and current density. Separation Science and Technology. 51 (1)
ABSTRACTThe graphite removal and the chemical oxygen demand (COD) reduction by the electrochemical treatment of an effluent containing a lubricant (oil in water emulsion with graphite) was investigated. The electrochemical cell used a pair of aluminum plates.Since the effluent conductivity was very low, NaCl was used as supporting electrolyte and different current densities as well as different distance between the electrodes were applied. In lower current densities, higher chloride concentrations implied in smaller COD values. The same behavior was observed when electrode distance was decreased. All the tested conditions presented significant graphite removal and COD reductions larger than 94%.
“…The (2 × 2) Al 2 O 3 slab is used to be the substrate for 1 to 12 Cl − adsorption in one ML plane, and the ML is from 1/28 to 12/28. The experimental and theoretical work [1,5,6,12,17,26,27] have improved that the most stable adsorption sites are Al(1) atop sites which are consistent with our calculations above, then the most stable configurations of ML = 1/28 to 4/28 are Al(1) atop adsorption. Because of the periodic expansion of slab, the most stable configuration in (1 × 1) slab is also the most stable configuration in (2 × 2) slab, this means the most stable configurations of ML = 8/28 and 12/28 are Al(1)B10 and O(5) adsorption.…”
Section: The Chloride Ions Adsorption On Supercell Of Al 2 O 3 Surfacesupporting
confidence: 82%
“…However, in environments that contain halogen anions such as chloride ions, the passive film becomes unstable and degrades locally causing film breakdown and pitting corrosion [1][2][3][4][5]. The interaction of chloride ions (Cl − ) on Al 2 O 3 surfaces represents one of the prototype examples of both surface science and electrochemistry [6].…”
“…[3][4][5][6][7][8][9][10][11] After all, localized corrosion can only occur if an otherwise protective passive film is present and undergoes a breakdown event. Studies have focused on linking film breakdown events to the composition and structure of the passive film using techniques such as X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM).…”
A debate about the critical step in localized corrosion has raged for decades. Some researchers focus on the composition and structure of the passive film associated with the initial breakdown of the film, whereas others consider that the susceptibility to pitting is controlled by the pit growth kinetics and the stabilization of pit growth. The basis for a unified theory of pitting is presented here in which pit stability considerations are controlling under aggressive conditions (harsh electrolytes and extreme environments and/or susceptible microstructures) and the passive film properties and protectiveness are the critical factors in less extreme environments and/or for less susceptible alloys.
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