Sometimes, despite best efforts, TMT rebars get rusted due to constant exposure to humid air or water. Rusting of TMT rebars can affect its performance. Further, it can affect the rib pattern on the TMR rebars that aid in gripping them to concrete.

Rusting should not be confused with scaling on the surface (usually referred to as mill scale). Moderate change in colour due to scaling on TMT rebar is quite common and does not affect its performance.

There are products available in the market for rust removal from TMT rebars. Some of them are as follows.

• Rusticide by Sunanda Global

http://www.sunandaglobal.com/Rusticide.pdf

• Rustoff 100 by Sika India

http://ind.sika.com/dms/211

• Reebaklens RR by Fosroc India

http://www.noblecorp.net/Reebaklens%20RR.pdf

In order to show the performance of these chemicals, we did a simple study. We took TMT rebars which have rusted. The image of these TMT rebars is below.

Rusted TMT rebars

Step I: Surface Preparation

We used a stiff wire brush to remove rust and other particles from the TMT rebar. After brushing, we used a dry cloth to clean the surface thoroughly.

Step II: Application of Chemicals

We used Reebaklens RR by Fosroc India for our study. As per instructions given by the manufacturer, we mixed Reebaklens RR with water in the ratio of 1:3 (1 part chemical with 3 parts water). As per the manufacturer, the ratio can be changed depending on the level of rusting. The thoroughly mixed mixture was applied on the TMT rebar with a paint brush. We made sure that the entire surface was wetted with the chemical mixture. After 60 minutes, we washed the TMT rebars thoroughly with clean water and used a wire brush to remove loose materials on the surface.

A TMT rebar of diameter 25 mm required around 50 ml of chemical. The cost of the chemical was Rs. 500 for 1 litre. The total time required was around 90 minutes including waiting period of 60 to 70 minutes.

The rust on the TMT rebar was removed by the process. It is to be noted that such products can remove rust and prevent further rusting for a few days. However, they cannot reverse the rusting process that has already taken place.

There are other chemicals available which can coat the surface of the TMT rebar after rust removal. These can also be used in case there is a chance of further rusting due to atmospheric condition, storage conditions etc. An example of such a product is Polyalk Fixoprime by Sunanda Global.

After doing this process, the result is shown in the image below.

TMT rebar, after treatment along with a section that was not treated.