Effect of composition and microstructure of duplex stainless steel on adsorption behaviour and efficiency of corrosion inhibitors in 4 molar hydrochloric acid. Part I: Standard DSS 2205

Highlights: • Variation in elemental composition on 6 batches of duplex stainless steel 2205 results in different uninhibited and inhibited corrosion rate. • The higher the Ni content, Ni/Cr ratio or austenite content, the lower is the weight loss. • Use of higher inhibitor dosage (20 mM) eliminates such dependence of weight loss on variation in the elemental compositions. • Cationic inhibitor preferentially adsorbs on ferrite phase (carbon concentration on ferrite phase is three time that on austenite phase measured by SEM-EDX). - Abstract: We investigate relationships between the elemental composition and microstructure of DSS 2205 materials and their acid corrosion behaviour (4 M HCl) in the absence and presence of inhibitor (naphthylmethyl quinolinium chloride, NMQCl). Without inhibitor, the corrosion rate decreases with increasing Ni and austenite content. The austenite content is mainly controlled by Ni and N contents. In the presence of inhibitor, at concentrations 4–11.1 mM, the corrosion rate decreases with increasing Ni content and inhibition efficiencies are 94.5–99%. When the inhibitor dosage is 20 mM, the corrosion rate becomes independent of Ni content and inhibition efficiencies are ≥99%.