Page 585 - Corrosion Engineering Principles and Practice

548 C h a p t e r 1 3 C a t h o d i c P r o t e c t i o n 549

13.4.2 Sacrificial Cathodic Protection
One alternative to impressed current CP is galvanic or sacrificial
anode CP. For steel in concrete, sacrificial anodes are typically made
of zinc or a zinc based alloy. While ICCP systems have been widely
used since the 1980s, sacrificial CP systems have only become available
around the end of the 1990s. Various configurations exist, including
• Thermal sprayed zinc, a few hundred microns in thickness
applied directly to the concrete surface (Fig. 13.21). A
humectant may be added for increasing moisture, reducing
concrete resistance, and increasing the current level.
• Thin sheets of zinc with a conductive adhesive backing
applied to the concrete surface.
• Expanded zinc mesh in a glass-reinforced plastic permanent
form filled with a proprietary cementitious grout, usually
applied to marine exposed piles in the splash and tidal zone.
• Zinc disks in a proprietary high alkaline mortar jacket
embedded in patch repairs to prevent the ring anode
or incipient anode effect discussed earlier in this section
(Fig. 13.22).
• Zinc plugs in a cylinder of a proprietary high alkaline mortar
for installation in cored holes in the concrete (Fig. 13.23).

FIGURE 13.21 Application of activated arc sprayed zinc on a reinforced
concrete structure. (Courtesy of Vector Corrosion Technologies)