Synergistic effect of polyaspartic acid and iodide ion on corrosion inhibition of mild steel in H2SO4

The inhibition effect of polyaspartic acid (PASP) and its synergistic effect with KI on mild steel corrosion in 0.5 M H2SO4 solution are studied by weight loss and electrochemical methods. The inhibition efficiency increases with the concentration of PASP and increases further with the presence of 1 mM KI. Result of the zero charge potential measurement shows that iodide ion promotes the film formation of PASP greatly. The mild steel surfaces after immersion test were analyzed using scanning electron microscopy and X-ray photoelectron spectroscopy. An adsorption model is proposed to elucidate the synergistic mechanism of synergistic effect.