11.1.10 Electrochemical Noise
Electrochemical noise is am onitoringt echnique that directlym easures
naturallyo ccurringe lectrochemical potential and current disturbances
because of ongoing corrosiona ctivity.I th as the same media conductivity
limitations and requirementf or ak nown electrode area as the other
electrochemical techniques. It is generally less quantitative than LPR for
corrosion rate calculations, and it is more useful in detection of transient
effects in marginally conductive situations. Laboratorya nd field interpretation is still ratherdevelopmental. Its proponents claim this techniquec an
provide al arge quantity of information that can be useful in determining
what is actually happening in real time with corrosion activity in the piping
or equipment beingmonitored. Detractors contend that there is, in fact, too
much information and especially analyze when therei sacontact but
acceptable level of corrosion activity in the system or another source of
potential electrical disturbance in the system.
This techniquem ay have merit as part of an on-site corrosion survey
conductedbys pecialists trained to interpret the data, but by no means is it
recommended as apermanent monitororasubstitutefor othertechniques.
TheC ORRATER
w
instruments operating in the “pitting index” or
“imbalance” modep rovide as imple electrochemical current noise sample
that is useful as an indicatorofp itting tendency or surfacei nstability.
11.1.11 Electrical Resistance
Electrical resistance (ER)p robes and instruments are basically “automatic
coupons” and share many characteristics with coupons, as discussed
above, when it comes to advantages and limitations. ER systemsw ork by
measuring the ER of at hin metal probe. As corrosion causes metal to be
removed from the probe, its resistance increases. The major advantage of
the ER method compared to coupons is that measurements can be obtained
on af ar more frequent basis and requirem uchl ess effort to make.W ith
automated systems,c ontinuous readings are, in fact,m ade, and sophisticated data analysis techniques are now available that permit the detection
of significant changesincorrosionrate in as little as 2hwithout generating
nuisance alarms.
11.1.12 CORROSOMETER
w
Systems
CORROSOMETER (ER) monitoringsystemscan be appliedtoall processes.
CORROSOMETER (ER) probe elements are available in avariety of styles. A
selectionofthe available styles is shown in Figure 11.1.Wire loop,tube loop,
and strip loop styles all have aloop of metal exposed to the process. The loop
protrudes from the end of the probe body through eitherahermetic glass
seal or aT eflon/ceramic, Teflon/epoxy,o repoxy seal/packing system.
Corrosion Monitoring
539
CAT8247—CHAPTER 11—6/10/2006—12:56—SRIDHAR—XML MODEL B–pp. 533–547
Electrochemical noise is am onitoringt echnique that directlym easures
naturallyo ccurringe lectrochemical potential and current disturbances
because of ongoing corrosiona ctivity.I th as the same media conductivity
limitations and requirementf or ak nown electrode area as the other
electrochemical techniques. It is generally less quantitative than LPR for
corrosion rate calculations, and it is more useful in detection of transient
effects in marginally conductive situations. Laboratorya nd field interpretation is still ratherdevelopmental. Its proponents claim this techniquec an
provide al arge quantity of information that can be useful in determining
what is actually happening in real time with corrosion activity in the piping
or equipment beingmonitored. Detractors contend that there is, in fact, too
much information and especially analyze when therei sacontact but
acceptable level of corrosion activity in the system or another source of
potential electrical disturbance in the system.
This techniquem ay have merit as part of an on-site corrosion survey
conductedbys pecialists trained to interpret the data, but by no means is it
recommended as apermanent monitororasubstitutefor othertechniques.
TheC ORRATER
w
instruments operating in the “pitting index” or
“imbalance” modep rovide as imple electrochemical current noise sample
that is useful as an indicatorofp itting tendency or surfacei nstability.
11.1.11 Electrical Resistance
Electrical resistance (ER)p robes and instruments are basically “automatic
coupons” and share many characteristics with coupons, as discussed
above, when it comes to advantages and limitations. ER systemsw ork by
measuring the ER of at hin metal probe. As corrosion causes metal to be
removed from the probe, its resistance increases. The major advantage of
the ER method compared to coupons is that measurements can be obtained
on af ar more frequent basis and requirem uchl ess effort to make.W ith
automated systems,c ontinuous readings are, in fact,m ade, and sophisticated data analysis techniques are now available that permit the detection
of significant changesincorrosionrate in as little as 2hwithout generating
nuisance alarms.
11.1.12 CORROSOMETER
w
Systems
CORROSOMETER (ER) monitoringsystemscan be appliedtoall processes.
CORROSOMETER (ER) probe elements are available in avariety of styles. A
selectionofthe available styles is shown in Figure 11.1.Wire loop,tube loop,
and strip loop styles all have aloop of metal exposed to the process. The loop
protrudes from the end of the probe body through eitherahermetic glass
seal or aT eflon/ceramic, Teflon/epoxy,o repoxy seal/packing system.
Corrosion Monitoring
539
CAT8247—CHAPTER 11—6/10/2006—12:56—SRIDHAR—XML MODEL B–pp. 533–547