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Tuesday, June 9, 2009 - 10:30 AM
EMP1.4

Electrodeposited Nanocrystalline Metals and Alloys as Environmentally Compliant Alternative Coatings to Functional Hexavalent Chromium and Cadmium

D. Facchini, J. McCrea, I. Brooks, F. Gonzalez, G. Palumbo, Integran Technologies, Inc., Toronto, ON, Canada

Increasingly stringent environmental and emissions requirements are putting severe pressure on the metal finishing industry to shift away from coatings that are deemed unacceptable from environmental, health and safety standpoints. These include Cd and hexavalent Cr plating which are used to provide corrosion and/or wear protection to aerospace components.

Electrodeposited Cd is used extensively by the aerospace industry to protect iron and steel from corrosion. Alternate coating technologies have found acceptance in various military and commercial Cd-replacement roles; however, there are still some technology gaps for specific applications, particularly regarding high-strength steel components which are prone to hydrogen embrittlement, a serious issue that commonly occurs in the corrosion-resistant coating process.

Hard Cr plating from hexavalent chromium solutions is a technique that has been in commercial production for over 50 years. It is a process that is used to apply hard coatings to a variety of aircraft components in manufacturing operations and for general re-build of worn or corroded components that have been removed from aircraft during overhaul. In particular, Cr plating is used extensively on hydraulic and pneumatic actuator wear surfaces. While HVOF coatings show good potential, their use has been limited because they are not amenable to non-line-of-sight applications and they require a fairly substantial investment in capital equipment.

Through microstructural design and engineering materials, Integran Technologies Inc. has recently developed several surface nanotechnology platforms as alternatives to existing functional Cr and Cd applications within the aerospace sector. An overview of nanocrystalline materials and their enabling structure/property relationships will be presented, with particular emphasis on processes and properties as they pertain to alternatives to Cr and Cd. For these examples the importance of application- and property-specific microstructural design and optimization is underscored.


Summary: Increasingly stringent environmental and emissions requirements are putting severe pressure on the metal finishing industry to shift away from coatings that are deemed unacceptable from environmental, health and safety standpoints. These include Cd and Cr plating which are used to provide corrosion and wear protection to aerospace components. Due to their unique properties and compatibility with existing electroplating infrastructures, electrodeposited nanocrystalline metal and alloy coatings represent an environmentally compliant alternative to Cd and Cr. An overview of nanocrystalline materials will be presented with emphasis on their processes and properties as they pertain to Cr and Cd replacement for aerospace applications.