  Corrosion of steel bars in reinforced cement concrete (RCC) structures leads
to premature deterioration and increase in life cycle maintenance costs.
Non-destructive testing (NDT) of incipient corrosion has been an impending task
in this domain. We present a low cost sensing platform based on eddy current
detection using anisotropic magnetoresistive (AMR) sensor to measure the extent
of corrosion in steel reinforcing bars (rebars). The scheme employs
phase-sensitive detection, wherein the phase shift in the sensor output
(proportional to surface conductivity of the rebar) relative to the reference
stimulus is measured by a lock-in amplifier and used to distinguish corroded
and non-corroded rebars. The proof-of-concept sensor demonstration is able to
resolve varying extents of rebar corrosion and can find potential applications
as an NDT tool in a variety of industries.
