Corrosion Inhibiting Admixtures for Reinforced Concrete—A State of the Art Report - Item No. 21428

Abstract

Introduction

Steel in concrete is normally protected from corrosion by the high pH of the concrete environment, which creates a stable passivation layer of iron oxides and hydroxides on the steel surface.

Chlorides, however, can penetrate this layer and soluble iron chloride complexes form that weaken this layer because of the increased solubility of the iron.

These iron chloride complexes allow iron to migrate from the bar surface outward in the cement paste, which leads to active ongoing corrosion of the steel.

Other causes of corrosion of steel in concrete are carbonation, galvanic attack between dissimilar metals, and stray current corrosion from external sources of direct current (see ACI 222R, ACI 201.2, and NACE Publication 01110).7,10,11

corrosion inhibitors for steel in concrete are generally tested with chlorides, and some have been evaluated for carbonation-induced corrosion.

Corrosion inhibitors for carbonation induced corrosion are discussed in Trabanelli (2005) and Söylev (2008).12,13 There is currently no technical information on the effectiveness of corrosion inhibitors for stray current or galvanic corrosion.

Corrosion reduces the cross-sectional area of the reinforcing steel and often leads to spalling of the concrete over it because of the increased volume of the corrosion products