Abstract:
Corrosion is a destructive process or degradation of metal quality because reaction with corrosive environment. Addition of inhibitors into corrosive media is one of the methods that able to decrease corrosion rate. Leaves of gambier is one of natural material which contains of tannin that able to be used as an inhibitor to protect metal from corrosion. The purpose of this research is to get the best concentration of inhibitor and inhibition efficiency of tannin extract from gambier leaves by varying the contact time and pH of corrosive media in decreasing corrosion rate. Tannin extract from leaves of gambier is obtained with soxhletation method by using methanol-water solvent with comparison 1:4 and then evaporated to get condensed extract of gambier leaves. Concentrations of tannin inhibitor that used are 1000, 3000, and 5000 ppm, with contact time variation are 5, 10, 15, 20 days, and variation pH of sea water as corrosive media are 3, 6, 9. Examination is conducted with gravimetry method to calculate weight loss of metal. The result of this research showed that lowest corrosion rate is 0,000547 gr/cm2.day at concentration of inhibitor 5000 ppm and contact time 20 days with average inhibition efficiency is 51,78%. At variation pH of sea water are obtained that lowest corrosion rate at pH of sea water ±9 is 0,000503 gr/cm2.day.
