<p>The synergistic effect of combining both Sida acuta (SA) and Jatropha curcas (JC) leaf extracts on steel in 1.0 M HCl solution was investigated using gasometric and conventional o o weight loss technique at 30 C and 50 C. Surface microscture of the steel with the mixed extract werestudied through Scanning electron microscope(SEM) and Electron dispersive X- ray spectroscopy (EDX) which revealed how the inhibitor hindered the attack of acid on the microstructures thereby preventing its dissolution into the corrodent. The presence of C=O -1 functional band at 1094 cm of ester was confirmed by Fourier transform infrared analysis. o o Synergism Parameter(S1) was at optimum at 2.09 and 2.65 at 30 C and 50 C respectively on steel pipe. This implies that synergism is favoured with increasein temperature. S1 greater than 1 confirmed that the mixture of the two plants produced synergised inhibitive effect. The inhibitory power increases with increase in extract concentration. Inhibition Efficiency -3 rangesfrom 60 % to 85 % with increasein extractconcentration of SAalonefrom 0.1 gdm to -3 o 1.0 gdm . When synergisedwith JC, itrangesfrom 77 % to 93 % for SA at 30 C forthesame concentration increase. Results obtained showed that thesynergeticeffects of the plantsextract complimented carbon constituent of the steel to enhanced the corrosion inhibition potential synergized plantextracts overunsynergized onthe steel.</p>