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Faraj A. Garman (PhD)
fargarmn@yahoo.com
Abstract
Cathodic protection of buried or submersed steel aims at reaching an absolute steel/environment potential of -850mV wrt. Cu/CuSO4. This criterion guaranties that the steel potential is driven into the immunity region of the Pourbaix diagram where corrosion of the steel is completely halted. Steel in concrete is in alkaline environment thus protected by the ferrous hydroxide film and corrodes only if this environment gets contaminated by aggressive species such as chloride ions, carbon dioxide and/or some other acid forming species. Corrosion protection in this case is achieved if the environment surrounding the steel is kept free of these species. The criterion for corrosion protection in this case has to be different. It has to aim at improving the environment surrounding the steel rebar rather than aiming at achieving an absolute potential shift. This paper presents field data and discusses the idea of establishing a new criterion for the corrosion protection of pre-stressed concrete cylinder pipelines based on the above mentioned facts.
Key words; Cathodic protection, Cathodic prevention, immunity, improving the environment.
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