Emerging Corrosion Control Technologies for Repair and Rehabilitation of Concrete Structures (page 5)


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Corrosion Special Topical Papers
Emerging Corrosion Control Technologies for Repair and Rehabilitation of Concrete Structures* Dr. Jianhai Qiu School of Materials Engineering Nanyang Technological University Nanyang Avenue, Singapore 639797 3.4 Snap-on Zinc Mesh Anode CP system 3.4.1 System Description This is yet another innovation in sacrificial anode cathodic protection system. The principle behind the system is exactly the same as that used by the zinc hydrogel anode system and the pre-packaged zinc anode system. This product was originally developed as "Lifejacket" by Alltrista Zinc products Company in North America and is marketed by FOSROC International as "Galvashield LJ". The all-in-one system (Fig.6) is based on the installation of 2-piece, snap-together jackets (Fig.7) lined with expanded zinc mesh (Fig.8). Fig.6 Snap-on Zinc Mesh Anode CP System (Galvashield LJ) (Photo copyrighted by FOSROC International and Alltrista Zinc Products Company) Fig.7 Fig.8 The two-piece fiberglass jackets snap together (Photo copyrighted by FOSROC International and Alltrista Zinc Products Company) Each jacket assembly is supplied with a minimum of 8 non-conductive standoffs per face. These standoffs secure the zinc mesh in place while achieving the optimum position of the jacket in relation to the piling.The self-contained system provides an innovative solution to the corrosion problems of both new and existing concrete structures subject to periodic wetting and drying as experienced in the splash and tidal zones (Fig.9). Fig.9 Zinc Mesh Anode Installed on Bridge Pilings (Photo copyrighted by FOSROC International and Alltrista Zinc Products Company) 3.4.2 Life Expectancy As in any other sacrificial anode CP system, the life expectancy can be calculated if current output of the anode is known. It is mainly determined by the amount of zinc anode material and the rate (current output) at which zinc “sacrifices” itself (in order to protect the cathode): Manufacturer’s data sheet suggests that the zinc mesh embedded in the snap-on fibreglass jacket has a projected life of 46 years. 3.4.3 Major Attractions and Applications Compared with conventional CP system, the snap-on zinc mesh anode jacket has the following attractions: All-in-one, self-contained sacrificial anode CP system Snap-on type quick, easy installation Low cost effective repairs Maintenance-free No need for external power Long life protection Jackets are available in a wide range of sizes and can accommodate both square and round pilings (Fig.10) Major applications include splash and tidal zones of steel reinforced concrete structures. Optional Cast bulk zinc anode can be used on fully submerged structures. Fig.10 Jackets for square and round pilings (Photo copyrighted by FOSROC International and Alltrista Zinc Products Company)
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