Abstract

The effect of Dimocarpus longan peel extract on the corrosion behavior of API 5L steel has been studied employing potentiodynamic polarization techniques and electrochemical impedance spectroscopy in an aqueous solution of artificial brine by injected CO₂ gas. The addition of that extract decreases corrosion rate of API 5L steel, increasing corrosion inhibitor efficiency of that up to an extract concentration of 400ppm. On the basis of result, corrosion inhibitor of Dimocarpus longan peel extract is categorized as mixed inhibitor type where both the decrease of anodic and cathodic current take place with increasing the concentration of inhibitor. A shift of corrosion potential for steel is below ±85mV vs saturated standard calomel (SCE) which refers to the presence of mixed inhibitor. Furthermore, the addition Dimocarpus longan peel extract also increase charge transfer resistance which indicates the formation of film due to molecule adsorption on the metal surface.

Keywords: Corrosion; Steel; Polarization; Impedance; Corrosion inhibitor