Efficiency of Cola acuminata Exudates as Corrosion Inhibitor for Mild Steel Pipes in Acid Concentrated Water and Soil

This study investigated the performance of Cola acuminata exudates in preventing mild steel exposed to acid concentrated water and soil. The study was performed in order to find an alternative coating substance that can reduce the corrosion of mild steel pipes exposed to corrosive water and soil media. Various mild steel specimens were cut into portions and coated with the exudates at 25 - 50µm thickness. To accelerate the rate of corrosion, 0.5M hydrochloric acid (HCl) was added to tap water in a container. Also, the same concentration of HCl was equally added to soil samples. Uncoated mild steel specimens were immersed in the acid concentrated water and soil, servicing as control sample. The rate of corrosion was monitored for 30 days (720 hours). The inhibition efficiency of the exudates for both corrosive media was compared. Results showed that the weight loss and corrosion rate of mild steel decreased with increase in coating thickness. Comparatively, weight loss and corrosion rate in the uncoated specimens were higher than the coated specimens. For uncoated specimens, the corrosion rate was 0.2793mm/yr and 0.4150mm/yr for specimen immersed in water and soil respectively, but at 25µm coating thickness, it decreased to 0.1516mm/yr and 0.2779mm/yr for specimens in water and soil. Also, at 50µm coating thickness, corrosion rate decreased to 0.0054mm/yr and 0.0308mm/yr for specimens in water and soil, respectively. The inhibition efficiency increased from 45.71 – 98.06% for specimens immersed in water and 33.11 – 92.57% for specimens buried in soil at 25µm – 50µm coating thickness. The results showed that Cola acuminata can serve as corrosion inhibitor for steel pipes exposed to corrosive media at minimum coating thickness of 35µm. Keywords: Mild Steel, Corrosion Rate, Cola acuminata Exudates, Water, Soil