Aging Behaviour of Zinc Spray Coating Applied for Cathodic Protection of Reinforced Concrete

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Title: Aging Behaviour of Zinc Spray Coating Applied for Cathodic Protection of Reinforced Concrete

Author(s): P. Delpire, G. Grimaldi, and A. Raharinaivo

Publication: Special Publication

Volume: 145

Issue:

Appears on pages(s): 871-882

Keywords: anodes; cathodic protection; concretes; corrosion; slabs; zinc; reinforced concrete; reinforcing steels; sprayed coatings; General

Date: 5/1/1994

Abstract:
For cathodic protection of reinforcing steel in concrete, a layer of zinc sprayed on the concrete surface can be used. This study presented the following concerns: the definition of concrete surface properties for adequate adhesion; the definition of the adequate spraying procedure, depending on the type of metal--pure zinc or zinc-aluminum alloy; the performance of cathodic protection systems in reinforced concrete slabs, under aging cycles. These slabs were stored outdoors. The aging cycles of the concrete slabs included: freezing during about 2 hr, by pouring liquid nitrogen on the surface of the slabs, so that a temperature gradient appeared in concrete; and thawing by natural heating, then by pouring water saturated with sodium chloride. This solution was then left flowing on the slab surface. The performance of the cathodic protection systems was checked by the usual procedures such as measuring the reinforcing steel potential and by checking the condition of the anode. It has been shown that cathodic protection can be fully achieved with zinc-spraying the concrete surface and application of impressed current. The experimentation on protection with sacrificial anode has given promising results. It also appeared that even when thin cracks are formed on the concrete surface, zinc spray coatings are still bonded, and the cathodic protection performances are changed only if cracks are wide enough to allow the salt solution to reach the embedded reinforcing steel.