Effect of Different Corroding Media on the Corrosion Rate of Locally Produced Thermo Mechanically Treated (TMT) High Strength Structural Steel Bar

Abstract

The corrosion behavior/rate of TMT steel bars in different corroding media such as rain water, storage atmosphere and concrete ponded in 10% sodium chloride solution has been investigated for a corrosion duration of 40 weeks. The corrosion rate of TMT steel bars corroded in the three media was measured at an interval of 4 weeks. Both macroscopy and microscopy were carried out to reveal different zones such as hardened case, soft core and transition zone in the cross-section and microstructure in these zones respectively of the TMT steel bars in the as received condition and after corrosion of 40 weeks duration. It was found that the corrosion rate of the TMT steel bars in rain water decreases gradually with corrosion duration and reaches a minimum value at 24 weeks of duration after which the corrosion rate increases. The corrosion rate of TMT steel bars in storage atmosphere initially increases and after reaching a maximum value at 16 weeks duration it starts decreasing. The corrosion rate of the TMT steel bars in concrete with 10% NaCl solution decreases very slowly and after reaching minimum value at 32 weeks of duration it starts increasing gradually. It was also found that the corrosion rate of the TMT steel bar in rain water is much higher than that of the TMT bar in storage atmosphere and the corrosion rate of the steel bars in concrete with NaCl solution is the lowest of all the media.