BASF Construction Chemicals’ Protectosil CIT, which offers a proven service life of more than 12 years, has taken silane concrete protection technology to new levels by offering the benefits of a corrosion inhibitor.

This single-component, ready-to-use, low viscosity, clear liquid combines the proven effectiveness of penetrative silane treatments for the control of moisture and chloride ion ingress with advanced organofunctional corrosion inhibition.
The use of silanes to protect reinforced concrete from the harmful effects of the ingress of water and chlorides was first patented in 1972. Since then, the chemists at BASF Construction Chemicals have been constantly improving the effectiveness of these “small but perfectly formed” molecules.   With the introduction of Protectosil CIT, they have taken the technology a major step forward by combining the known benefits of the silane molecule with an effective corrosion inhibitor.
 
Corrosion
The mechanism of corrosion of reinforcement steel in concrete is well documented in the Arabian Gulf, such that in the presence of aggressive chloride ions (or carbonation of the concrete), electrochemical reactions lead to dissolution of the steel and formation of oxides of iron.  During the process, there is no net consumption of chloride ions so these remain in place, promoting localised pitting corrosion, which can rapidly reduce the integrity of steel cross-sections and structural integrity. Only water and oxygen are needed to continue the reaction.

Use of silanes
Since the 1970s, silanes have provided engineers and owners with one of the most cost-effective methods of protecting reinforced concrete.  The silane molecule can be synthesised with a variety of reactive sub-groups that modify the behaviour and performance in concrete. Changing the length of the molecular chain of the reactive group will alter such behaviour as reaction speeds, volatility and penetration depths.  Over the past 20 years, silanes have been used as water repellents to protect reinforced concrete from the harmful effects of waterborne chloride ions. 
Long-term on-site testing has shown how effective corrosion inhibitor treatments based upon silanes can be in halting corrosion in existing structures or delaying the outset of corrosion when applied to new structures, even in the most aggressive of environments such as oil facility foundations, sea walls and jetties in industrial locations.  Silane materials are successful because they:
•  Have small reactive molecules with very low viscosity and surface tension;
• Penetrate deep into the concrete;
• Chemically bond with silaceous materials within concrete;
• Chemically bond with iron oxide layers;
•  Reduce water ingress (and therefore waterborne chlorides) by more than 90 per cent.

Organofunctional groups
For more than a decade, chemists have been synthesising silane molecules with one of the alkoxy reactive groups replaced by organic subgroups that provide additional benefits to the engineer.  For example, when an organofluoro molecule (similar to those used in non-stick coating applications) is grafted onto the basic silane backbone, additional benefits such as reducing the adherence of paints are provided.  In this way, excellent anti-graffiti properties are produced.
The most exciting breakthrough was achieved by synthesising a silane molecule that includes an active corrosion inhibitor incorporating organo-amine (R-NH2) groups.  Most amino-containing, topically-applied corrosion inhibitors rely upon the high volatility of the organic molecules to migrate through the concrete cover to the steel where the NH2 groups are then able to strengthen the passivating layer at the steel surface. However, some researchers have noted that this volatility leads to concerns of loss of effectiveness due to evaporation, especially in a highly humid environment.
Protectosil CIT is so effective because the silane backbone chemically bonds to the cementitious matrix, hence it is permanently bonded within the concrete and cannot evaporate or be leached from the substrate.

Conclusion
Independent field studies in Europe and the US support the impressive independent laboratory data showing the effectiveness of Protectosil CIT of not only preventing corrosion in new structures but also of effectively halting existing corrosion in structures.  Protectosil CIT prevents further corrosion caused by the formation of incipient anodes around newly-installed patch repairs.
With a proven service life of more than 12 years and an expected life of 15 to 20 years, Protectosil CIT is a simple-to-use, cost-effective weapon in the fight against chloride or carbonation induced corrosion.
Protectosil CIT is sprayed directly onto the surface of steel reinforced concrete structures and buildings.
It is equally suited to cast-in-situ, precast, post-tensioned, prestressed, GFRC (glass-fibre reinforced concrete), or other steel reinforced concrete.
It is particularly suited for the protection of: Bridge decks, piers columns and beams; multi-storey car-parks, building facades and balconies; and marine jetties and structures.
Protectosil CIT can be used as part of an overall repair strategy using Emaco concrete sytems to mitigate  corrosion rates within the balance of the structure and significantly reduce the possibility of  “ring anode“ induced spalling at a later date.
When a fully monitored and permanent solution (25-plus-year life) is required, even with very high chloride concentrations, it can be combined with other solutions such as the Emaco CP range.  In addition, complementary protective coating systems are also available to enhance the aesthetics of the structure.   These systems provide the very highest levels of protection in the challenging environments found in the Middle East region.