Resources

Luz Marina Calle¹, Rubiela D. Vinje², and Louis G. MacDowell¹

¹NASA, YA-F2-T, Kennedy Space Center, FL, 32899, U.S.A.

²Dynacs, Inc., DNX-15, Kennedy Space Center, FL, 32899, U.S.A.

 

Abstract

Space organizations face the difficult challenge of protecting launch pad structures from corrosion. Thin gauge steel and aluminum structures such as protective bellows around drive mechanisms flex repeatedly and thus require highly flexible and adherent coatings. The aerospace industry has traditionally used paints having high volatile organic compound (VOC) content for protecting vehicles and support structures. Flexible paints employ solvent borne rubber binder resins, which render the products highly viscous and difficult to apply by spraying. Waterborne elastomeric anticorrosion coatings are being developed for the corrosion protection of metals such as aluminum and steel in corrosive environments. The ultimate goal in developing the coatings is to provide an effective and environmentally sound method for protecting the surfaces of aluminum and steel without introducing additional pretreatment and priming steps. EIS, corrosion potential measurements, and visual observation were used to evaluate the corrosion protection properties of an experimental formulation of a primerless silicone coating on aluminum 2024-T3, stainless steel 316, and cold-rolled steel. EIS spectra as well as corrosion potential measurements were collected at 24-hour intervals for 168 hours in 3.5% aerated NaCl. Panels of the bare alloys, as well as panels of stainless steel 304 and aluminum 2024-T3, coated with an aluminum-filled nitrile rubber coating (AR-7) were also included in the investigation.

The newly developed primerless silicone coating was effective at the corrosion protection of stainless steel 316 but failed on aluminum 2024-T3 and cold-rolled steel. The failure was greater in the case of the cold-rolled steel. Corrosion potential as well as impedance measurements and visual observations indicate that the aluminum-filled nitrile rubber coating provides a superior degree of corrosion protection on aluminum 2024-T3 than on stainless steel 304.

Keywords: EIS, silicone coatings, corrosion, aluminum 2024-T3, stainless steel 304.

For additional information, a complete copy of this study is available as NASA Report.  Send requests for copies to corrosion@ksc.nasa.gov.
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