A comprehensive study on the adsorption, corrosion inhibition efficiency and stability of acriflavine on mild steel in 1 M HCl solution

A comprehensive study was conducted on the adsorption, corrosion inhibition efficiency and stability of acriflavine (ACF) on mild steel (MS) in 1 M HCl solution. Electrochemical studies were conducted to determine the corrosion protection ability of the inhibitor after short and long immersion times. The MS surface after exposing to the uninhibited and inhibited solutions were characterized by SEM, EDX, AFM and contact angle measurements. The excess surface charge of the metal and some thermodynamic parameters were derived after 1 h and 6 h exposure times and a possible adsorption and inhibition mechanism was discussed. The electrochemical stability of the inhibitor film formed on the metal surface was studied using potentiodynamic and potentiostatic techniques. It was found that ACF adsorbs on the MS surface via dominantly chemical and weakly physical interactions and forms a protective surface film. The film was adherent, uniform, protective and electrochemically stable. The inhibitor film provides maximum inhibition efficiencies of 92.8% and 97.1% at 1 mM after 1 h and 6 h immersion times. ACF mitigates the rates of both anodic metal dissolution and cathodic hydrogen evolution reactions. The excess surface charge of the steel in the inhibited solution was negative, which becomes more evident after longer exposure time.