The criterion used to verify the cathodic protection condition of a structure is based on structure-to-electrolyte potential measurement, which can include an ohmic drop contribution. Among the available techniques, the use of potential probes with internal reference electrode and of corrosion coupons with a so-called soil-access tube represents the most appropriate way to measure the IR-free potential, eliminating the ohmic drop contribution. An alternative is represented by on-off technique if equalising, galvanic or stray currents are not present. Laboratory tests have been carried out in soil-simulating solution on cathodically protected carbon steel in order to evaluate the effectiveness of off-potential for the assessment of cathodic protection. Instant-off potential is not reliable in overprotection condition; moreover, the accuracy of the measurement is strongly influenced by the presence of external current as galvanic or equalising currents. The effect of low-pass filter in the data acquisition system on the potential reading is discussed.

Cathodic protection monitoring of buried carbon steel pipeline: measurement and interpretation of instant-off potential

BRENNA, ANDREA;BERETTA, SILVIA;UGLIETTI, RICCARDO;LAZZARI, LUCIANO;PEDEFERRI, MARIAPIA;ORMELLESE, MARCO
2017-01-01

Abstract

The criterion used to verify the cathodic protection condition of a structure is based on structure-to-electrolyte potential measurement, which can include an ohmic drop contribution. Among the available techniques, the use of potential probes with internal reference electrode and of corrosion coupons with a so-called soil-access tube represents the most appropriate way to measure the IR-free potential, eliminating the ohmic drop contribution. An alternative is represented by on-off technique if equalising, galvanic or stray currents are not present. Laboratory tests have been carried out in soil-simulating solution on cathodically protected carbon steel in order to evaluate the effectiveness of off-potential for the assessment of cathodic protection. Instant-off potential is not reliable in overprotection condition; moreover, the accuracy of the measurement is strongly influenced by the presence of external current as galvanic or equalising currents. The effect of low-pass filter in the data acquisition system on the potential reading is discussed.
2017
Carbon steel; cathodic protection; hydrogen overvoltage; instant-off potential; monitoring; ohmic drop; protection potential; Chemistry (all); Chemical Engineering (all); Materials Science (all)
File in questo prodotto:
File Dimensione Formato  
Full manuscript_on-off CEST.pdf

Accesso riservato

Dimensione 1.77 MB
Formato Adobe PDF
1.77 MB Adobe PDF   Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1033100
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 12
  • ???jsp.display-item.citation.isi??? 5
social impact