http://www.corrosion-doctors.org/Advances/DaicEIS.htm

Conventional EIS requires immersion of a specimen into an
electrolyte and the use of remote counter and reference electrodes.
This procedure is suited for the laboratory as long as small
specimens and immersion conditions are suitable for the study. The
new, in-situ corrosion sensor technology addresses these issues and
allows EIS measurements to be taken in the field or laboratory under
ambient or accelerated testing conditions. The new technology is
suitable for coated metals, composites, and adhesive bonds. As such,
it extends the applicability of EIS to aging structures enabling
condition-based maintenance (CBM) and to coating development and
screening in exposures ranging from ambient to salt fog (ASTM B117)
to cyclic accelerated testing (e.g., Prohesion, Ford APG, GM 9540P,
and SAE J2334).