Preventing Corrosion of Embedded Metal 

Mechanism
The role of the chloride ion in inducing reinforcement corrosion is well documented. Chloride ions can enter into the concrete from deicing salts that are applied to the concrete surface to melt snow and ice or from seawater in marine environments, including air-borne chlorides. Other sources of chloride ions include admixtures made with intentionally added chlorides, chloride-contaminated aggregates and/or mixing water, salts in ground water, and salts in chemicals that are applied to the concrete surface.  Without treatment, these chlorides react with the embedded reinforcing metals in concrete.  This reaction process creates significant stresses in the concrete, deteriorating the integrity of the concrete structure.

Prevention
Chloride–induced corrosion can be controlled and durability improved by utilizing BASF's corrosion-inhibiting admixtures and supplementary cementitious materials.

The Rheocrete^® family of corrosion inhibitors offers options to prevent corrosion of steel reinforced concrete structures.

• Rheocrete CNI   admixture is a proven, inorganic anodic-type corrosion inhibitor. The nitrite ions in Rheocrete CNI admixture react with ferrous ions to form an oxide film at the steel surface that increases the resistance of the steel to chloride attack.
• Rheocrete 222+    admixture is a proven, organic-based amine-ester corrosion inhibitor that provides "superior" protection in cracked concrete. Rheocrete 222+ admixture functions by lining the capillary pores with a hydrophobic layer that effectively reduces concrete permeability and by forming a protective film at the steel surface.

Silica Fume can also enhance the corrosion protection and improve the durability of concrete structures:

• Rheomac SF 100 silica fume reduces concrete permeability by providing additional hydration product that reduces the number and size of capillary pores.

Technical Papers and Articles

• Wiss, Janney, Elstner Associates (WJE) Report – Use of Rheocrete 222+ in High Performance Concrete 
• Long-Term Effectiveness of Corrosion-Inhibiting Admixtures and Implications on the Design of Durable Reinforced concrete Structures: A Laboratory Investigation – Nmai and McDonald
• Multi-Functional Organic Corrosion Inhibitor – Nmai
• NACE Corrosion 92 "Effect of Chemical"
• April 1, 1992 Concrete International "Organic-Based Corrosion-Inhibiting Admixture For Reinforced Concrete"
• 1999 RILEM International "Long-Term Effectiveness of Corrosion-Inhibiting Admixtures and Implications"
• March 1, 1998 ACI Structural Journal "Predicting the Service Life of Concrete Marine Structures: An Environmental Methodology"
• Materials Week 2000, International Congress on Advanced Materials "Long-Term Performance of an Organic Corrosion Inhibitor: A Decade of Mechanism Study"