Inorganic Coatings for Thermal and Corrosion Control of Al-Mg Alloys
Abstract
The total ownership costs for Naval vessels primarily reside in operations and sustainment.Aluminum marine alloys promise to reduce these costs through their lighter weight, weldability,machinability, recyclability, strength, and corrosion resistance. Long used in the deckhouses ofUS Navy vessels, 5000 series Al-Mg alloys now comprise the entire structure of theIndependence Class Littoral Combat Ship (LCS).Their impressive corrosion resistance of was once thought to obviate the need for painting.Unfortunately, the very mechanism responsible for these properties???solid solutionstrengthening???renders 5083 and 5456 Al susceptible to thermal sensitization. The surfacetemperature of aluminum routinely rises 40??C above ambient in direct sunlight. Suchtemperatures cause the electrochemically active ??-phase (Al3Mg2) to precipitate at grainboundaries from a supersaturated Al-Mg solid solution, making these grain boundaries prone tointergranular corrosion. In order to maintain the full benefit of the 5000 series Al-Mg alloys, it istherefore necessary to implement a coating system that can maintain the temperature below 40??Cand enhance its inherent corrosion resistance without adding significant weight to the vessel.JHU/APL therefore proposes a silica/polysiloxane coating system that maintains aluminum ata low temperature, even in direct sunlight, by rejecting solar radiation while efficiently emittinginfrared radiation at longer wavelengths. Due to the unique inorganic primer, the coatingautonomously repairs itself through water-assisted reconstruction. It goes beyond thecapabilities of existing self-healing coatings by healing in response to corrosion activity inaddition to mechanical damage.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 26, 2018
- Source ID
- N000141712399
Entities
People
- Jason J Benkoski
Organizations
- Johns Hopkins University
- Office of Naval Research
- United States Navy