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Title: Durable Hydrophobic Coating for the Remote Minehunting Tow Cable

Authors: Adam Goff (Luna Innovations), Bryan Koene (Luna Innovations), Hillary Rees (Luna Innovations), Rebecca Martin (Luna Innovations), and Luke Logan (Lockheed Martin)

The outer cable strands used to tow the AQS-20A from the Remote Multi-Mission Vehicle (RMMV) are made from Nitronic 50, an austenitic stainless steel that, under normal circumstances, exhibits excellent corrosion resistance and strength over a wide temperature range. Unfortunately, some cables have experienced early life corrosion problems due to salt water deposit buildup that occurs over repeated operations and subsequent system stowage. To achieve the corrosion and abrasion resistance necessary for the AQS-20A tow cable, Luna is collaborating with Lockheed Martin to develop a hydrophobic watershedding coating that is mechanically durable, optically transparent, and easy to apply. There have been many recent research and commercial efforts in the area of hydrophobic or water repellent coatings that have demonstrated the ability to shed fluids quickly off of surfaces. Whereas many surface treatments and coatings have achieved the primary goal of good fluid shedding properties, they have all lacked mechanical / environmental durability, or are difficult and expensive to apply. Luna’s new polymer-inorganic hybrid coating has a unique combination of fluid repellency and exceptional toughness for improved abrasion resistance and environmental stability. The coating formulation can be easily applied in a single step by dip, flow, brush, or spray and it possesses low surface energy leading to easy cleaning and excellent corrosion resistance. In addition to good fluid shedding properties, the coating has significantly higher density than traditional organic polymer coatings and is electrically insulating, resulting in improved barrier properties to water and corrosive ion permeation. 

The presentation will review the hydrophobic coating chemistry and a variety of performance test results. The formulated coating has been demonstrated to significantly boost the corrosion protection of the tow cable and stand up to repeated cyclic testing using surrogate sheaves representative of the Remote Minehunting System (RMS) cable handling system. A custom accelerated corrosion test method developed to assess the corrosion resistance of cable sections will be detailed, along with corresponding bare and coated cable test results. In addition, an application process will be presented that has been developed to apply the coating to the tow cable in a continuous fashion.

The presentation will conclude with a summary of future work that will be carried out under the project, including next-steps in coating development and how this new coating may be used to mitigate metallic corrosion across the Navy. 

This work is being funded by NAVSEA under Contract No. N00024-15-C-4005.