Effect of henna at high concentration in methanol for the inhibition of aluminium in seawater

Abstract

Aluminium Alloy 5083 or known as AA5083 has been a well known material in shipbuilding for a couple of decades because it owes its outstanding corrosion resistance. But nowadays corrosion is an obscure or untraceable threat to all industries that related to metal, in marine industry, corrosion effect the hull, piping system, equipments and other material related to metal. Hence, to overcome this using inhibitors are one of the most practical methods for protection against corrosion. In this experiment, henna extract was used. Hence it is classified as natural inhibitor. Henna also known as Lawsonia ineremis. Henna leaves were immersed in methanol for a week before it was filtered and extracted using rotovap. The henna extract was observed using fourier transform infrared spectroscopy (FTIR). The concentration used were high concentration, they were 600ppm, 700ppm, 800ppm, 900ppm and lOOO ppm. The duration for the immersion period was 60 days. The coupons were tested for loss weight experiment, electrochemical test (potentiodynamic polarization (PP) scan, electrochemical impedance spectroscopy (EIS)) and one time for scanning electron microscope (SEM). From FTIR observation shown the abundant element content in henna extract was Lawsone. The values of inhibition efficiency percentage, IE (%) were obtained from weight loss, corrosion current density, Icorr, polarization resistance, R,,, and corrosion rate, CR , parameter. The IE% results shown as the concentration of henna was increased, the IE% was increased. The corrosion rate, CR results analysis show, the corrosion rate increases again immersion period.