Cathodic protection (CP) coupons and soil corrosion probes (SCPs) can be effective tools in
applying CP criteria under challenging operating environments. These situations include measuring offpotentials
using coupons in cross-bonded systems or structures influenced by interference from CP
systems not controlled by the main protected system operator, or where CP potentials cannot be
reliably measured and corrosion rate measurements using electrical resistance (ER) soil corrosion
probes are used as an alternative to conventional CP criteria for buried pipelines.
This paper looks at the various scenarios where CP coupons and SCPs can be used, using field
data from installations on buried pipelines, and also with reference to the requirements of the new ISO
standard ISO/FDIS 15589-1 on different CP criteria for varying soil resistivities. Information is also
given on the recent work by the NACE International Technical Committee TG-321 draft report on soil
corrosion probes.