| Smart Coatings: The use of
"smart materials" for corrosion sensing purposes relies on a material undergoing
a transformation through its interaction with the corrosive environment. It is such
transformations that can potentially be used for indicating and detecting corrosion
damage. Ideally, in principle, the sensing function could be integrated with additional
actuation and control functions, designed to control corrosion damage.
Several initiatives have been launched on the front of using smart coatings as
corrosion sensors, but presently the technologies reside mainly in the experimental
laboratory domain. As such, they are "futuristic" in nature.
Some smart coating principles, including
those relevant to corrosion sensing, or potentially relevant, include the following:
Paint systems with color-changing compounds, responding to pH changes
that result from corrosion processes.
Changes of coating compounds from non-fluorescent to fluorescent states,
upon oxidation or complexing with metal cations.
Release of color dyes, on coating damage, from incorporated dye-filled
micro-capsules.
Use of pigments that absorb corrosive chemicals - a news release from
Ohio State University likened this concept to "high-tech kitty litter".
Use of pigments that release corrosion inhibiting chemicals "on
demand".
Piezo-electric thin film applications.
Fiber optics
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References/Literature:
R.E. Johnson and V.S. Agarwala: "Using Fluorescent Compounds as Early Warning
Detectors for Corrosion, Materials Performance, April 1994, pp.25-29.
R.E. Johnson and V.S. Agarwala: "Fluorescence Based Chemical Sensors for Corrosion
Detection", Corrosion 97, NACE International, New Orleans, 1997.
J. Zhang and G.S. Frankel: "Investigation of the Corrosion-Sensing Behavior of an
Acrylic-Based Coating System", Corrosion, 1999, p.957.
Links:
"Corroded planes turns pink" by C. Wu at:
www.sciencenews.org/sn_arc97/12_6_97/fob2.htm
Some general thoughts by "Dr. Tomorrow" at:
www.coatingsmagazine.com
select the Nov/Dec 99 issue and "Tomorrow's Technologies"
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