Pitting inhibition of newly developed lean duplex stainless steel 2002 in NaCl solution by a green inhibitor

Abstract

The pitting inhibition of sodium lignosulphonate (SL) on newly developed lean duplex stainless steel (LDSS) 2002 in 3.5% NaCl was assessed by using various electrochemical methods. The electrochemical results reveal that the critical pitting temperature (CPT) of LDSS 2002 decreases with increase in inhibitor concentration. The breakdown potential (Eb) also decreases with inhibitor addition and the initiation of metastable pittings is effectively suppressed. The potentiostatic pulse technique (PPT) shows that the propagation of pitting and initiation of pitting location can slightly be influenced by addition of SL. The adsorption of SL on the LDSS 2002 surface in 3.5% NaCl solution follows the Langmuir adsorption isotherm and the adsorption accords with both physical and chemical adsorption process. Meanwhile, the presence of SL acts as a barrier to the adsorption and/or penetration of chloride ion into the passive film, thereby inhibiting the pitting initiation and growth.