Cathodic protection by impressed DC currents for construction, maintenance and refurbishment in reinforced concrete
✍ Scribed by H. McArthur; S. D'Arcy; J. Barker
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- English
- Weight
- 1015 KB
- Volume
- 7
- Category
- Article
- ISSN
- 0950-0618
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✦ Synopsis
This paper models the pH changes which occur when reinforced concrete structures are cathodically protected by an externally applied DC current. It is shown that the cathodic area is initially made very alkaline immediately after switch-on, and the anodic area becomes acidic in nature. This acidic area spreads out from the anodic electrode towards the cathodic area. It is found that this alkalinity is produced at the cathodically impressed rebar as the impressed current (a) uses up the dissolved oxygen; (b) requires the hydroxyl ions to carry the ionic current; (c) produces hydrogen. In conclusion, for cathodic protection to work effectively there must be a way for oxygen to diffuse to the cathodic area, so that it takes part in the cathodic reaction. The anodic area becomes acidic and the alkaline OHions are moved away from the rebar as a requirement for continuous current flow.