Page 152 - Corrosion Engineering Principles and Practice

126 C h a p t e r 5 C o r r o s i o n K i n e t i c s a n d A p p l i c a t i o n s o f E l e c t r o c h e m i s t r y 127

Surface mounted Coating/paint
coating integrity
monitor
Sensing element (conducting metal tape)

Metal substrate
(a)

(b)
FIGURE 5.31 (a) Schematic of the coating health monitor (CHM) with a tape
sensing element mounted on a coated metal and (b) actual sensor tape
electrode and electronics housing mounted on the frame of a commercial
vehicle. (Courtesy of Guy D. Davis, DACCO SCI, Inc.)

occurring fluctuations do not have controlled frequencies as are
applied, for example, in EIS.
There are basically three categories of ENA: visual examination,
sequence-independent methods that treat the collection of voltage or
current values without regard to their position in the sequence of
readings (moments, mean, variance, standard deviation, skewness, and
kurtosis), and those that take the sequence into account (autocorrelation,
power spectra, fractal analysis, stochastic process analysis) [22].