ABSTRACT
The effectiveness of Terminalia catappa (tropical almond) and Tamarindus indica (tamarind) as corrosion inhibitors for stainless steel in 1M hydrochloric acid at 30°C, 40°C and 50°C was investigated in this research. The gravimetric method of analysis was employed for 20 days at a 4-day interval using 0.9, 1.1 and 1.3g/15mL of Terminalia catappa leaves extracts and 1.4 and 2.3g/15mL of Tamarindus indica leaves extracts. The results showed that the two extracts acted as good inhibitors for stainless steel. The corrosion rate, surface coverage, inhibition efficiency, inhibition mechanism and the effects of temperature were analyzed. The results showed that the highest inhibition efficiency for tamarind was 97.71% at 30°C using 2.4g/15mL, while the lowest was 87.95% with 2.3g/mL at 30°C.The highest efficiency for tropical almond was 97.89% with 1.3g/mL at 50°C and the lowest was 88.7% with 0.9g/mL at 50°C. The isotherms showed that tropical almond acted as a mixed type inhibitor, although predominantly by physisorption. The effects of temperatures also confirmed that tamarind adsorbed by physisorption only.