Monitoring cathodic protection of buried pipeline by means of a potential probe with an embedded zinc reference electrode. (15th January 2017)

• Record Type: Journal Article
• Authors: Brenna, Andrea; Lazzari, Luciano; Pedeferri, MariaPia; Ormellese, Marco
• Is Part Of: Materials & design. Volume 114(2017)
• Page Start: 194
• Page End: 201
• Publication Date: 2017-01-15
• Subjects: Cathodic protection -- Potential -- Probe -- Ohmic drop -- Monitoring -- Zinc; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2016.11.089
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: According to international standard, cathodic protection efficiency is controlled by monitoring IR-free potential. Nowadays commercial probes are available to perform correct potential reading, eliminating the ohmic drop contribution. In this paper, a new probe with a zinc reference electrode embedded in a proper backfill is proposed. Zinc is a promising material due to the low overvoltage in active condition and the high exchange current density. Laboratory tests were performed to select a stable backfill, in order to avoid any risk of shrinkage and mass loss. Sixteen mixtures based on gypsum, clay and other additives were considered. Gypsum, specifically sulfate ions, were used to maintain zinc in active condition; bentonite, absorbing humidity from the surrounding soil, guarantee a constant proper level of water content. Four additives, pure cellulose, an air-entraining agent, expanded glass granules and silica-based sand, were added to study the effect on water absorption, mass loss and electrical conductivity. Two of them were selected to prepare two probe prototypes with incorporated zinc electrode in order to verify the stability of both backfill and zinc during continuous cathodic protection monitoring. Graphical abstract: Highlights: A potential probe with a Zn reference electrode embedded in a proper backfill is proposed to monitor cathodic protection The probe allows measuring potential eliminating the ohmic drop contribution, as requested by international standard Backfills are based on a mixture of gypsum, bentonite and cellulose in order to retain water and reduce mass loss Backfills avoid shrinkage and guarantee a good electrolytic contact between zinc electrode and carbon steel plate