TPS II is a solution  of water soluble silicates plus activators  and migratory aids made by a process that creates a variety of reactive silicate structures.  It is applied to the surface of reinforced concrete to inhibit corrosion, increase strength  and reduce porosity. TPS XII is water solution  of an organic vapor phase migratory corrosion inhibitor. They are two of 20 products made and supplied by Surtreat for the restoration and protection of concrete and masonry structures.  TPS II is designed to furnish a broad spectrum of performance while the others are designed to focus on specific problems.

 

The performance of TPS II and TPS XII occur in three physical and chemical steps.

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1.   Inoculation into the concrete cement phase micro pore structure. This occurs in the liquid phase to a depth of about 0.25 to 0.5 inches by direct application to the surface.

2.   Migration in the ionic phase in the water film on the cement micro or gel pore surfaces.

Migration has been verified to a depth of 2 to 3 inches by reductions  in rebar corrosion rates and water soluble chloride concentration at these depths.

3.    Reaction with the ferrous hydroxide film on the rebar steel surface to form a ferro­

silicate complex which increases the resistance to corrosion, and a reaction  with the water soluble chlorides to form an insoluble complex with the cement.  TPS II also reacts near the concrete surface with the cement free alkali sites to form a solid phase that reduces porosity  and increases strength.

 

These functional steps are verified by physical and chemical measurements  made before and after application. The Appendix includes sections from reports on the performance of TPS II (aka GPHP) and TPS XII (aka TPS V or VCI) with respect to the reduction in rebar corrosion  and water soluble chloride  concentration.

 

Changes in porosity  and surface strength occur in a few days while changes in corrosion rate and potential, and water soluble chloride  concentration take place gradually over a 2 to 3 month period.  Changes in porosity  and surface strength occur primarily in the liquid phase

inoculation zone while the reduction in corrosion and water-soluble chlorides occur beyond this

zone in the deeper ionic and vapor phase (TPS XII) migration zones.

 

The time related migration process is verified by the rate at which the corrosion half cell potential and corrosion current  change with time.  The time related change in rebar corrosion using TPS II and the organic vapor phase migratory inhibitor TPS XII has been documented in several independent laboratory studies performed by NASA at the Kennedy Space Center,The Korean Construction Technology Research Institute and The Rand Afrikaans University.

 

 

Sections from these reports  are in the Appendix and present plots of half cell potential and corrosion current  with time starting with the fresh concrete  and moving through the corrosion activation stage by chloride  (salt) exposure and application of TPS II and TPS XII (TPS V). The plots show that it takes between  60 to 90 days for the rebar corrosion condition, at 1to 2 inches of cover, to return to the original passive state.  The vapor phase migratory inhibitor takes the same time period as the ionic migratory inhibitor TPS II to reach the rebar level and create a passive state.

 

Also attached are pages from a Wiss Janney report  on evaluation  of corrosion inhibitors applied to a building and 2 bar graph plots of corrosion rate measurements made by Corrosion Control Technology (CCT) before and after application of TPS II.  The Wiss Janney plot shows the same time related change in corrosion rate.  The CCT bar graphs show that TPS II has

significantly reduced the anodic corrosion hot spots and that the reduction is much greater than the reduction in average corrosion rate.  This is what is expected for an ionic anodic type of inhibitor like TPS II.  If the reduction in corrosion rate by TPS II was only due to the reduction in porosity  and a subsequent reduction in water and oxygen concentration at the rebar level, the change in corrosion rate should take place in a much shorter time and the change in corrosion rate should be more like the effect of a cathodic inhibitor that would predomonately reduce the average rate across all of the corrosion measurement points.

 

The results are attached of an impressed current  corrosion test developed by Florida DOT (FM 5-522) performed by the University  of Florida Department of Civil and Coastal Engineering. It shows a significant increase in the time to failure for the cell treated with TPS II as measured by a sudden sharp increase in the impressed current. Besides the average 85% improvement in durability that could be explained by a reduction in porosity  there was a significant  reduction in the current  during and after failure between  the treated and untreated samples indicating that TPS II had changed the surface of the rebar imbedded at 2 inches and had made the

pass-avating film more resistant to chloride attack and decomposition that would lead to further

rebar corrosion.

 

During the past 20 years Surtreat has performed many projects on reinforced concrete structures  using TPS II and TPS XII where before and after application rebar corrosion  potential and rates were measured.  One such project  was performed for the Corps of Engineers in Okinawa during 2006. Corrpro Corp was retained  in 2010 to reevaluate  the treated structures with respect to rebar corrosion  rate.  The attached segment from their report  shows that the initial corrosion rate was 2.4 micro meters per year (mpy), that  it had dropped to 0.96  in 6 months  and had decreased to 0.55 mpy 3 years latter  in 2010. This shows that the TPS II and TPS XII applied in 2006 have continue  to migrate and decrease the rebar corrosion over this extended time period.

 

Besides the corrosion rate plots the Korean study showed that TPS II (GPHP) reduced the concentration of water soluble chlorides by 33% at 30mm or 1.2 inches. PSI (see attached reports  segment) applied TPSII (GPHP) to concrete slabs that had been exposed to a salt solution. The water soluble chloride content  at 2 inches from the surface was 0.33 wt.% and dropped to O.llwt.% after application. The change is due to the formation of an insoluble complex with TPS II and the cement 2 inches below the surface.