Chemical conversion coating for protecting magnesium alloys from corrosion

US9228263B1 · kind B1 · utility

Assignee

• Nei & Company Inc. · US

Inventors

• Gaurang Bhargava · Monmouth Junction, US
• Fred M. Allen · Princeton Junction, US
• Ganesh Skandan · Easton, US
• Peter Hornish · Lincoln, US
• Mohit Jain · Bengaluru, IN

Key dates

• Filing date: Oct 22, 2012
• Grant date: Jan 5, 2016
• Expiry date: Oct 20, 2033

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C23C22/40
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

A chromate-free, self-healing conversion coating solution for magnesium alloy substrates, composed of 10-20 wt. % Mg(NO3)2.6H2O, 1-5 wt. % Al(NO3)3.9H2O, and less than 1 wt. % of [V10O28]6− or VO3− 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.