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Chemical conversion coating for protecting magnesium alloys from corrosion

United States Patent

January 5, 2016
View the Complete Patent at the US Patent & Trademark Office
A chromate-free, self-healing conversion coating solution for magnesium alloy substrates, composed of 10-20 wt. % Mg(NO.sub.3).sub.2.6H.sub.2O, 1-5 wt. % Al(NO.sub.3).sub.3.9H.sub.2O, and less than 1 wt. % of [V.sub.10O.sub.28].sup.6- or VO.sub.3.sup.- dissolved in water. The corrosion resistance offered by the resulting coating is in several hundreds of hours in salt-spray testing. This prolonged corrosion protection is attributed to the creation of a unique structure and morphology of the conversion coating that serves as a barrier coating with self-healing properties. Hydroxoaluminates form the backbone of the barrier protection offered while the magnesium hydroxide domains facilitate the "slow release" of vanadium compounds as self-healing moieties to defect sites, thus providing active corrosion protection.
Bhargava; Gaurang (Monmouth Junction, NJ), Allen; Fred M. (Princeton Junction, NJ), Skandan; Ganesh (Easton, PA), Hornish; Peter (Stewartsville, NJ), Jain; Mohit (East Brunswick, NJ)
NEI Corporation (Piscataway, NJ)
13/ 656,963
October 22, 2012
STATEMENT OF GOVERNMENT SUPPORT OF INVENTION The work leading to the present application was done as part of Department of Energy Grant Number: DE-FG02-08ER85204, the government has certain rights in the invention.