China
Africa
Explore chapters and articles related to this topic
Role of Surfactant in Other Organs
Published in Jacques R. Bourbon, Pulmonary Surfactant: Biochemical, Functional, Regulatory, and Clinical Concepts, 2019
In both of the foregoing industrial examples, the use of simple inorganic phosphate precludes the simultaneous use of a cationic surfactant which can also provide corrosion protection and lubrication. The problem of using both together is that, whereas the phosphate provides good cohesion, it is poorly adsorbed so it cannot be laid down first, but if the strongly adsorbed cationic is laid down first, then its outwardly orientated hydrophobic moieties will repel any attachment of the phosphate layer. This problem of providing double protection may have been solved by the body in a most ingenious way.3,7
Aircraft Decontamination and Mitigation
Published in Brian J. Lukey, James A. Romano, Salem Harry, Chemical Warfare Agents, 2019
William T. Greer Jr., Angela M.G. Theys, William R. Davis, Kenneth J. Heater
To mitigate these challenges, hardware designers can, to a degree, address the chemistry of the threat by employing techniques for both conventional chemicals and chemical warfare hazards. Today, aircraft and systems that deploy globally must deal with a wide range of environmental chemicals that can corrode materials. Pollutants such as ozone and NOx can slowly eat away at exposed materials, and operating in salt air environments can corrode exposed metals. This damage is evidenced by billions of dollars spent annually on fighting corrosion from many environmental sources. From a corrosion prevention perspective, one key tool is employing coatings to protect materials from environments that degrade substrates over time. These coatings, designed to provide corrosion protection, can also serve as barriers to control agent absorption. For example, CARC, which was originally designed to resist chemicals, also serves to mitigate corrosion, thus reflecting dual roles on equipment. CARC formulations continue to evolve to improve its protective properties (Escarsega and Smith, 2009).
From laboratory tests to field trials: a review of cathodic protection and microbially influenced corrosion
Published in Biofouling, 2022
A. A. Thompson, J. L. Wood, E. A. Palombo, W. K. Green, S. A. Wade
An added reaction resulting primarily from the change in pH during CP is the forced precipitation of the calcium and magnesium in seawater onto the surface of protected metals once pH reaches 9.3 or greater (Barchiche et al. 2009). These precipitates, commonly referred to as calcareous deposits, build up over time on the surface of protected metals, often initially as thin layers of Mg(OH)2 with thinner layers of CaCO3 developing with ongoing protection (Neville and Morizot 2002). These deposits are non-conductive and reduce the effective surface area of metals that can be corroded. This reduction of surface area also decreases the number of sites at which biofilms can form directly on the metal surface, which may lower the likelihood/extent of MIC. Furthermore, calcareous deposits are able to act as a barrier against exposure to oxygen and the wider environment, reducing oxygen diffusion to the metal surface and lowing the possible occurrence of corrosion. As more deposits develop, less metal remains exposed and as such less protection is required, this reduces the total current demand required to maintain protection, making the process of CP more efficient (Wolfson and Hartt 1981). While it can be advantageous to have calcareous deposits form, it is not guaranteed that the layer will prevent corrosion and growth of the deposits can be slow or patchy, leaving sections of metal exposed (Vasyliev and Vasylieva 2020). In some cases, it has also been noted that the calcareous deposits can aid in the adsorption of microbes to the surface (Zhang et al. 2020). In contrast, it has also been seen that microbes have helped develop more consistent calcareous layers improving overall corrosion protection (Dexter and Lin 1992).
A comparison of the antifouling performance of air plasma spray (APS) ceramic and high velocity oxygen fuel (HVOF) coatings for use in marine hydraulic applications
Published in Biofouling, 2018
Richard Piola, Andrew S. M. Ang, Matthew Leigh, Scott A. Wade
Maritime hydraulic machine components, including exposed sections of shafts, splines and valves, can often see regular wetting and drying or full immersion in seawater. This leads to potential problems with biofouling and corrosion on these critical components, which require costly repairs to bring the equipment back to operational performance. One potential solution to this issue is the use of an engineered coating layer that offers high wear resistance as well as biofouling and corrosion protection.
Probing the correlation between corrosion resistance and biofouling of thermally sprayed metallic substrata in the field
Published in Biofouling, 2022
Pedro A. Vinagre, Johan B. Lindén, Enara Mardaras, Emiliano Pinori, Johan Svenson
For marine renewable energy (MRE) devices, biofouling thus represents a key challenge. Such devices must be operational offshore for 10–20 years and they are not designed to have dry-dock intervals (Macleod et al. 2016; Vinagre et al. 2020; Want et al. 2021). MRE devices and associated structures are starting to be deployed at half and full scale and the sector is expected to play an important role for future energy supply (Soukissian et al. 2017; Weiss et al. 2018; Copping et al. 2020). New material challenges arise and optimized material selection needs to perform well as retrofitting and remediation in offshore environments can be very costly (Mérigaud and Ringwood 2016; Vinagre et al. 2020). Among the various challenges faced by the MRE sector, the synergy between biofouling organisms and marine corrosion is one major challenge for structure reliability in harsh marine conditions (Titah-Benbouzid and Benbouzid 2015; Loxton et al. 2017). The offshore oil and gas sector have longstanding experience with corrosion and harsh marine conditions (Hartt 2012). Here, thermally sprayed aluminium (TSA) has been successfully used to combat steel corrosion at near sea level structures and for seawater intakes (Echaniz et al. 2019; Syrek-Gerstenkorn et al. 2020). The TSA coating consists of an aluminium layer deposited by thermal spray techniques on steel surfaces to be protected (Echaniz et al. 2019; Syrek-Gerstenkorn et al. 2019). The TSA layer corrodes in seawater and is consumed at a predictable rate of <10 µm year−1 (Syrek-Gerstenkorn et al. 2020). Therefore, a typical coating thickness of 200–300 µm can provide >25 years of protection (Fischer et al. 1995). Moreover, TSA displays unique self-passivation properties not obtainable with most organic coatings(Echaniz et al. 2019). The sacrificial metallic coating offers both barrier properties and cathodic protection. As the sacrificing TSA is consumed, aluminium hydroxides and oxides precipitate on top of the coating. If damage to the coating occurs through, for example, erosion or microbiological effects, a galvanic couple between aluminium and the steel substratum is established due to the potential difference between the two metals. Cathodic reactions of oxygen reduction and hydrogen evolution will take place on the steel surface, forming OH− ions and locally increasing pH close to the steel surface. This series of events triggers precipitation of calcareous deposits (magnesium hydroxide and calcium carbonate) at the cathodic site. Although TSA has shown good long-term corrosion protection performance and being frequently used for protection of offshore steel structures, the corrosion protection mechanism is not completely understood (Fischer et al. 1995; Grinon-Echaniz et al. 2021a).