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Corrosion Causes and Cures
Published in Jerry P. Byers, Metalworking Fluids, Third Edition, 2018
Copper is only slowly corroded by acids and alkalis, though fatty acids present in many cutting fluids can react to form pale green soaps. However, fatty acids are unlikely to cause the corrosion or discoloration of copper during the short time that they are in contact while machining. Copper is discolored though by the formation of copper sulfides due to a reaction between certain sulfur-containing compounds that can be present in cutting fluids. The problem is not insuperable however, since there are several extremely effective copper corrosion inhibitors that can be in corporated into a cutting fluid. These generally act by forming a molecular layer of an insoluble organic compound over the entire copper surface. Benzotriazole and similar organic molecules are widely used as copper corrosion inhibitors. Only small amounts are required to be effective, but they do deplete with time and may need to be replenished.
Advanced Micro/Nanocapsules for Self-healing Smart Anticorrosion Coatings
Published in Hatem M.A. Amin, Ahmed Galal, Corrosion Protection of Metals and Alloys Using Graphene and Biopolymer Based Nanocomposites, 2021
Kayla Lee, Cynthia G. Cavazos, Jacob Rouse, Xin Wei, Mei Li, Suying Wei
Polyelectrolyte multilayer nanocontainers for self-healing anticorrosion coatings contain inhibitors meant to heal or prevent any corrosion caused to the surface of a material, in this case metals. They must be compatible with the type of nanocontainer used, in this case polyelectrolyte multilayer. The inhibitors also benefit more if they can prevent or stop a type of corrosion that correlates to how the nanocontainers are broken open. These inhibitors are the main agent that prevent corrosion from taking place by patching up any holes in the coating caused by chemical or mechanical damage. One inhibitor is benzotriazole (BTA). Benzotriazole is used as a corrosion inhibitor for metal and metal alloys including copper, aluminum, iron, and zinc. When released, it creates a passive layer that prevents corrosion. Benzotriazole is useful for conditions that offer external andic polarization. A major drawback of BTA is that it is water-soluble, but when used with polyelectrolyte nanocontainers inside a coating this drawback is lessened [49]. Benzotriazole is used as an inhibitor since it is great at covering any openings the coating may obtain due to damage, thus making it self-healing. The effectiveness of benzotriazole varies immensely with different concentrations, sizes, and layouts of the nanocontainers encapsulating it. Large mechanical damage may cause issues with coatings that rely only on BTA, since BTA may not be able to cover all the damage. Large scale damage is also an issue with many inhibitors since there is only so much an inhibitor can cover. BTA has been tested to work well for prolonged periods in a corrosive environment when used with a well-made nanocontainer and coating [54]. 2-mercatobenzothiazole (MBT) was tested as a potential inhibitor. MBT self-heals by forming a thin film on an alloys surface protects the surface against corrosion. MBT is notably a good inhibitor for aluminum alloys. MBT is not an effective anti-corrosive inhibitor when used outside of nanocontainers. MBT does not affect adhesiveness of coatings that are using it. 2-methylbenzothiazole and 2-mercaptobenzothiazole work well against corrosion caused by small mechanical damage. Both do not work well against constant salt sprays as it can be possible for them to remove any new barrier formed. This was tested with a salt spray test and every case showed no inhibition to corrosion and received a macro rating of 5 [51]. Diagram of a polyelectrolyte nanocontainer formed by layer-by-layer absorption using poly sodium 4-strenesulfonte (PSS) and poly diallyldimethly ammonium (PDADMAC). The nanocontainer shown contains the corrosion inhibitor 2-mercatobenzothiazole (MBT) [51].
Performance of commercial LDH traps for chloride ion in a commercial corrosion protection primer for petrochemical industry
Published in Corrosion Engineering, Science and Technology, 2020
Andrea Renata Deip, Débora Abrantes Leal, George Hideki Sakae, Frederico Maia, Marcos Antonio Coelho Berton, Mário Guerreiro Silva Ferreira, Cláudia Eliana Bruno Marino
Benzotriazole (BTA), which is an organic nitrogen-based molecule, has been widely used as corrosion inhibitor [19]. However, the direct addition of BTA in the coating is not effective, since this inhibitor is water soluble and leaves empty voids in the coating layer, which can decrease the protective barrier of the coating [15,20]. Kamburova et al. [21] reported that hematite nanoparticles were encapsulated with polymers for application as nanocontainers that can release the entrapped BTA in response to pH changes in the environmental medium. Other works have also demonstrated BTA responsive release by changing the pH of the solution [14,22]. However, in all these reported works, it is necessary to modify particles or to realise complicated syntheses to obtain a stimuli-responsive behaviour from the particles. On the other hand, layered double hydroxide has a stimuli-responsive intrinsic property due the characteristic ion-exchange behaviour of this material that depends on the ionic concentration of the media.
A review on the removal of conditioning chemicals from cooling tower water in constructed wetlands
Published in Critical Reviews in Environmental Science and Technology, 2018
Thomas V. Wagner, John R. Parsons, Huub H. M. Rijnaarts, Pim de Voogt, Alette A. M. Langenhoff
Benzotriazole and its derivatives are commonly used organic corrosion inhibitors in cooling towers and due to its omnipresence in surface waters globally, its environmental fate and biodegradability is well studied (Giger, Schaffner, & Kohler, 2006; Reemtsma, Miehe, Duennbier, & Jekel, 2010). The fate of benzotriazole in CWs has been subject of multiple studies resulting in conflicting removal efficiencies from 6% to 93% (Felis, Sochacki, & Magiera, 2016; Kahl et al., 2017; Matamoros, Jover, & Bayona, 2010; Matamoros, Rodriguez, & Albaiges, 2016; Matamoros, Rodriguez, & Bayona, 2017), which were attributed to different removal mechanisms. The CWs in the study by Matamoros et al. (2017) showed a benzotriazole removal of 9%. The CWs in that study are already functional for over 10 years. In contrast, higher benzotriazole removal rates were of >75% were found in the 5 year old traditional and intensified CWs in the study of Kahl et al. (2017), which were attributed to biodegradation. However, only comparing influent and effluent concentrations is not suitable for the determination of a removal pathway in a constructed wetland, given the fact that multiple removal pathways could play a role in benzotriazole removal. It is known that benzotriazole is taken up and transformed by plants (Castro, Davis, & Erickson, 2004), while benzotriazole has also shown to adsorb to sediments (Hart, Davis, Erickson, & Callender, 2004). Nevertheless, both the CWs in Kahl et al. (2017) and Matamoros et al. (2017) are planted with Phragmites australis, so the large difference in removal efficiency cannot be attributed to phytodegradation. A possible explanation could be that quick adaptation of the microbial community in the CWs in Kahl et al. (2017) resulted in higher biodegradation rates. In addition, the substrate in the latter CWs could have a higher adsorption affinity and/or capacity for benzotriazole.