SENSITIVE COLORIMETRIC DETECTION OF EARLY STAGES OF ALUMINUM CORROSION BY GOLD ISLAND FILMS

Aluminum is the metal-of-choice in a wide range of applications thanks to its low weight, superior mechanical strength, malleability and easy machining, corrosion resistance, high thermal and electrical conductivity, and low neutron absorption cross-section. However, corrosion of aluminum components upon exposure to high temperatures and/or corrosive environments is a major reason for the failure of various metallic parts and equipment. Therefore, convenient monitoring of the surface condition of aluminum parts in-service is of vital importance.

The special optical properties of metal (Au, Ag) nanostructures, attributed to excitation of localized surface plasmons (SPs), result in strong light scattering, intense SP absorption bands, and enhancement of local electromagnetic fields. These properties have been employed in optical devices, surface enhanced spectroscopies, and in chemical and biological sensing.^[1] Here we show application of the sensitivity of localized surface plasmon resonance (LSPR) spectroscopy to dielectric changes at the metal nanostructure–ambient interface for real-time monitoring of the surface condition of aluminum, in particular the progress of corrosion. Sensing of the corrosion process is based on the change of the effective dielectric constant in the vicinity of gold nano-islands deposited on a defined area of the aluminum surface, resulting from growth of an oxide film on the metal surface. Development of the oxide can be monitored either using standard spectroscopic equipment, or, in some cases, with the naked eye. The advantage of LSPR-based corrosion monitoring is the versatility of the technique, which can be used in variable environment (solution, gas) and temperature, as well as operated remotely in real-time when the relevant surface is unreachable.

[1] A. Vaskevich, I. Rubinstein, in Nanoplasmonic Sensors, (Ed: A. Dmitriev), Springer: New York, 2012, 333.