Cathodic Protection (corrosion control) of Reinforced Concrete Structures Using Conductive Coatings

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Title: Cathodic Protection (corrosion control) of Reinforced Concrete Structures Using Conductive Coatings

Author(s): Joseph A. Lehmann

Publication: Special Publication

Volume: 102

Issue:

Appears on pages(s): 127-142

Keywords: cathodic protection; chlorides; coatings; reinforced concrete; reinforcing steels; sulfates; Materials Research

Date: 9/1/1987

Abstract:
Usually concrete is an ideal environment for steel. Reinforcing Steel in most concrete structures is not subject to corrosioin. However, when salts (chlorides or sulfates) penetrate concrete and reach steel rebars, corrosion becomes active. Rust takes up a larger volume than the iron from which it is formed, developing pressure as great as 5000 psi within the concrete. This pressure causes cracking and spalling. Ultimately, failure occurs and major repair or replacement is needed. Once salts (from deicing, bleaching, marine environment, foreign aggregate etc.) contaminate concrete, corrosion progresses rapidly. Penetrants, sealants, surface coatings, and membrane barriers are useless in combatting the effects of salts already in concrete. The use of cathodicprotection to control corrosion on reinforcing steel in concrte is relatively reinforcing steel in concrete is relatively new. Although cathodic protection has been employed on pipelines, offshore cathodic protection has bee employed on pipelines, offshore platforms, ship hulls, buried tanks, etc. for more than 40 years, its use on concrete bridge decks was initiated only in the early 70's. Since the development of conductive coatings (1980-82) the effectiveness of cathodic protection has been enhanced.It has become easier to install and is now applicable to many different types of concrete structures (i .e ., docks; harbor facilities marine terminals; bridge substructures such as piers, pier caps, and beams; bulkheads; parking garages; industrial water and waste treatment plants; tunnels coastal buildings, etc. acceptance ofconductive coating cathodic protection continues to grow , new applications develop. This new form of an established technique holds extraordinary promise for large-scale preservation of concrete structures. (SP-102