Multifunctional rare earth organic corrosion inhibitors

MARKLEY, CSIRO Materials Science and Engineering, Australia, F. BLIN, AECOM, Australia, M. FORSYTH, DeaMnUniversity, Australia and B. HINTON, Monash University, Australia. 

Key words multifunctional inhibitors, rare earth, oiganic, steel, aluminium. 

Developing effective corrosion protection systems for a range of metallic alloys has been a significant research focus for many decades. This is because although the alloying process improves the physicochemical properties of the base metal, it often increases the metal s susceptibility to corrosive attack (Fig. 4.1). If measitres are not taken to protect these alloys from their corrosive 

1 Pitting corrosion of aluminium alloy 2014-T6. Reprinted with permission of ASM International. All rights reserved. www.asminternational.org. 

As discussed in other chapters of this book, corrosion inhibition by rare-earth containing species has been investigated as an alternative system to the environmentally hazardous chromate coatings. Rare earth species have proven to be effective corrosion inhibitors for steel, zinc and aluminium.  

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Multifunctional rare earth organic corrosion inhibitors... 

There are advantages and inherent limitations associated with the use of multifunctional rare earth organic inhibitors for corrosion protection, with the most obvious advantage being the decreased toxicity of these compounds compared with chromate species. This reduced toxicity makes this class of corrosion inhibitors attractive in an industrial sense, as less health and safety issues would arise during manufacture, application and repair. There would also be fewer adverse environmental impacts to consider. 

The sparing solubility of these multifunctional inhibitor compounds lend themselves more readily to incorporation into paints as slow-release corrosion protection. To avoid possible interference of rare earths elements with epoxy polymer coating systems, as has been observed, an encapsulation mechanism may be considered to successfully incorporate rare earth organic inhibitors into paint formulations. This would limit any detrimental interaction, while still allowing the release of an inhibitor as required. 

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