Materials Research

Magnesium Rich Coatings for Corrosion Control of Reactive Metal Alloys

EPA Grant Number: X83254101-1

Center: CEER at Alfred University

Investigator: DeRosa, Rebecca

Institution: Alfred University, School of Engineering

Project Period: September 1, 2006 – February 28, 2008

Research Category: Congressionally Mandated Center

Description:

To date, hexavalent chromium is the most effective inhibitor of corrosion for aluminum, steel and magnesium alloys.  Yet, since 1982 the use of chromates and other chromium-containing compounds has been limited due to their carcinogenic effects.  It is believed that the environmentally friendly formulation of inorganic magnesium rich coatings can provide exceptional protection for aluminum and magnesium based alloys and will be the next alternative to chromates.  Our work will focus on  the analysis of metal rich coatings using electrochemical and surface analysis techniques to determine their effectiveness as corrosion protective coatings on reactive metal alloys.

Objectives/Hypotheses:

We are testing Mg rich coating systems as possible chromate replacement coatings for corrosion control of reactive metal alloys. The hypothesis is that the Mg particles embedded in an inorganic matrix coating will sacrificially corrode and provide extended corrosion protection to the underlying metal substrate.

Approach:

The immersion of a material in an electrolyte allows an in-situ characterization of the surface state of that material and its evolution. That surface state can be determined by different electrochemical techniques like open circuit potential measurements, polarization measurements and impedance measurements. The information obtained by such in-situ electrochemical techniques can be linked to ex-situ surface characterization techniques, like scanning electron microscopy, x-ray photoelectron spectroscopy and atomic force microscopy. In that way, a global insight on the degradation and protective processes taking place during corrosion can be obtained.  Metal rich coatings will be analyzed using these techniques to determine their effectiveness as corrosion protective coatings. 

Expected Results:

Magnesium rich systems as chromate replacement coatings show great promise.  Because the idea is in its infancy there is a lot of work that needs to be done on formulation and testing of the MRC systems.  The work described here will not be the end, only the beginning to the study of these new coatings.  In the end, the impact will be greatly rewarded.  This is evident by the interest other agencies have in finding a suitable chromate replacement coating.  The Air Force Office of Scientific Research has set aside a portion of their funding to support the first two years of the Center for Surface Protection existence directly supporting basic research in corrosion protective aircraft coatings.  The Air Force Research Laboratory – Materials and Manufacturing Directorate has much of their funding set aside for development and scale-up of Mg-rich Cr-free primers for aircraft to assist the Air Force in meeting Environmental Protection Agency and Occupational Safety and Health Administration requirements.  In addition, the Air Force Research Laboratory and Coatings & Polymeric Materials has $125,000 in FY06 for scale-up and flight testing of the Mg-rich primer technology for military aircraft. 

Supplemental Keywords:

corrosion, metal rich coating, magnesium rich coating, aluminum alloy, magnesium alloy

CEER is funded in large part by the United States Environmental Protection Agency.

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