Corrosion-Inhibiting Admixtures: Passive, Passive-Active Versus Active Systems

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Title: Corrosion-Inhibiting Admixtures: Passive, Passive-Active Versus Active Systems

Author(s): C. K. Nmai

Publication: Special Publication

Volume: 154

Issue:

Appears on pages(s): 565-586

Keywords: admixtures; chlorides; corrosion; reinforced concretes; size screening; Materials Research

Date: 5/1/1995

Abstract:
In this paper, corrosion-inhibiting admixture systems are classified as active, passive, or passive-active, depending on the mechanism(s) by which corrosion inhibition is achieved. Also, a simple analytical equation that relates chloride ion contents in treated concretes to that in companion untreated concrete is presented. Using this equation, chloride ion content versus screening efficiency curves have been for passive and passive-active inhibitor systems. If chloride ion threshold and chloride screening efficiency data are available, these curves can be used to determine and "equivalent chloride ion threshold" for passive and passive-active inhibitor systems and to compare directly the effectiveness of passive and passive-active inhibitor systems on time-to-corrosion relative to active inhibitor systems. Corrosion test data have been used to show the validity of this analytical procedure. The data show that the procedure can be used to rank the effectiveness of corrosion-inhibiting admixtures in delaying the time-to- corrosion of steel in concrete and that passive and passive-active inhibitor systems can delay the onset of corrosion longer than active inhibitor systems. In combination with corrosion rate data, the relative overall effectiveness of corrosion-inhibiting admixtures can be determined.