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Corrosion of Pipeline Steels in Slurry of Thermal Power Plant : A Case Study

Himanshu Shekhar Shukla, Nilesh Haldar and G. Udayabhanu

Corrosion of slurry handling systems is a serious problem and failure of pipelines transporting slurries can result in shutting down of the whole operation causing huge financial loss to the industry. Keeping the above in view the present investigation was planned for studying the corrosion behavior of two commonly used pipeline materials, namely cast iron and mild steel, in fly ash slurries at different concentrations and pH values. The results of the corrosion rate study of mild steel and cast iron in fly ash slurries at five different concentrations from 10% to 50% w/v and in water at pH 6 for durations of 3 and 6 hours were carried out. Experiments were conducted to ascertain the corrosion rates of mild steel and cast iron in water at three different pH (pH = 6, 7 and 8). These experiments were repeated in 20% fly ash slurry adjusted to the above pH values. Scanning Electron Microscopic study of mild steel and cast iron before and after corrosion in 20% fly ash slurry adjusted to pH 6, 7 and 8 have been done. Varying the pH of the slurry had a significant effect on the corrosion rates. Maximum corrosion rate for mild steel was observed at pH 8 with the order pH 8 > pH 6 > pH 7 and for cast iron at pH 6 with the order pH 6 > pH 8 > pH 7. Scanning Electron Microscopy of corroded samples show that damage caused is more extensive in cast iron than mild steel under similar conditions. This might be due to the more heterogeneous microstructure of cast iron compared to that of mild steel.