The deterioration of aluminium alloy in 2.5 M hydrochloric acid in the presence Rauvolfia vormitoria
extract was examined using both gasometric and gravimetric techniques. Aluminium coupons measuring
4 cm by 1 cm were introduced into test solutions of uninhibited acid and also those containing extract
quantities of 10, 20, 30 and 40 cm3 at ambient temperature of 250C for a total cumulative period of 117
minutes. The volumes of hydrogen gas evolved and weight loss readings were recorded and analyzed to
obtain weight loss and corrosion rate for each coupon at specific time intervals. The results however,
showed that while extract quantity was increasing; weight loss measurements increased but inhibitor
efficiency decreased. Also, the metal surface-phytoconstituent interaction mechanism was consistent with
the Temkin adsorption isotherm and the 3 minutes curve showed the best exposure time for
phytochemicals to adsorb to alloy surface. Furthermore, microstructural studies showed an indirect
relationship between metallic degradation and extract quantity, while uniformity of the irregular
intermetallic phases increased with increasing extract quantity
