A fight worth fighting for….
By Niteen Jadhav, Andrew Brentano, and Robert Azevedo
The great destroyer, the evil, the passive menace. A defiant, dangerous, ruthless, unrelating, pervasive, and invisible enemy. A subtle and silent foe. It has been called various names by a great many¹. It cannot readily be perceived or easily seen. It is said that it never sleeps! We are not talking about formidable physical foes or disruptive biological agents; we are talking about “rust” or, more technically, “corrosion”. Corrosion of metals and their alloys has serious ramifications that cost the Unites States more than the damage inflicted by all natural disasters put together each year. Our modern civilization is built with metals and corrosion impacts transportation, utilities, health care, defense and more. To put this in economic terms, in the year 2013 the worldwide cost of corrosion was about 3.5% of total GDP or approximately 2.5 trillion USD².
Corrosion happens spontaneously. Elements such as iron and oxygen are more highly reactive than end corrosion products (rust). To make matters worse corrosion reactions typically generate heat, further accelerating the ongoing reaction, all in accordance with the second law of thermodynamics. Metal alloys are produced from metal ores using a tremendous amount of energy through the process of refinement in massive smelting furnaces and forges. In the presence of oxygen and water, these metals have thermodynamic tendency to revert back to their native oxide state by releasing the energy put in during formation³. Therefore, corrosion is a natural and self-sustaining process. Owing to this thermodynamic favorability, it is impossible to stop corrosion. In more philosophical terms: everything that has been created will be destroyed, though time scales may vary. However, the very nature of corrosion processes also paves the way for identification, mitigation, prevention, and avoidance. Today corrosion is tackled with corrosion resistant alloys, improved mechanical designs, Cathodic/Anodic protection, coatings and paints, corrosion inhibitors and other methods. Coatings, a physical barrier, are generally considered the first line of defense against corrosion.
Modern society depends on the use of HVAC- R appliances for comfort and survival. Corrosion of heat exchanger coils inside HVAC-R devices causes performance degradation, refrigerant leaks, heat transfer efficiency losses from the insulating effects of built up corrosion products, and marred appearance of appliances⁴. In highly corrosive environments, a nearly 50% reduction in performance, capacity, and utility of appliances has been observed within just one year of operation⁵. Current coating solutions for HVAC-R rely heavily on petrochemical based coating systems which have poor thermal conductivity, reduced heat transfer efficiency, increased air resistance (reducing efficiency), reduced frost performance, and relatively short-term corrosion performance.
At Nelumbo, we attacked this challenge head-on and have developed proprietary technologies that demonstrate improved corrosion protection and enhanced ice and condensate management properties⁶. Nelumbo technologies are inorganic and ultrathin, solving typical efficiency and heat transfer problems, and enabling conformal coverage of complex objects with many edges, a game changer for the industry. These binder-free surface modifications impart different surface structures resulting in novel properties. Several chemistries are available which are scalable and do not involve any toxic volatile solvents in processing. Each of these elements is key to ensuring the entire lifecycle of the solution is sustainable and environmentally friendly. Our goal is to see these products make a significant contribution to performance and energy savings for HVAC-R systems worldwide, a major step forward for climate solutions.
Acknowledgements:
Authors would like to thank Nelumbo Inc management for the support and encouragement in publishing this article.
References:
¹ J. Waldman, Rust: The Longest War, Simon & Schuster, 2015. https://books.google.co.in/books?id=fs0NBAAAQBAJ.
² G. Koch, J. Varney, N. Thompson, M. Moghissi, J. Payer, International Measures of Prevension, Application, and Economics of Corrosion Technologies Study, 2016. http://impact.nace.org/documents/Nace-International-Report.pdf.
³ N. Jadhav, C.A. Vetter, V.J. Gelling, The effect of polymer morphology on the performance of a corrosion inhibiting polypyrrole/aluminum flake composite pigment, Electrochim. Acta. 102 (2013) 28–43. https://doi.org/10.1016/J.ELECTACTA.2013.03.128.
⁴ N.F. O’Neill, J.M. Ma, D.C. Walther, L.R. Brockway, C. Ding, J. Lin, A modified total equivalent warming impact analysis: Addressing direct and indirect emissions due to corrosion, Sci. Total Environ. 741 (2020) 140312. https://doi.org/https://doi.org/10.1016/j.scitotenv.2020.140312.
⁵ A. Bhatia, HVAC Design Considerations for Corrosive Environments, (2019). https://www.cedengineering.com/courses/hvac-design-considerations-for-corrosive-environments (accessed June 19, 2021).
⁶ Nelumbo Inc, (n.d.). https://www.nelumbo.io/ (accessed June 19, 2021).
