Corrosion behaviour of 110SS steel in hydrochloric acid–acetic acid composite system

The objective of this study is to investigate the corrosion behaviour of 110SS carbon steel in a hydrochloric acid–acetic acid mixed system, with dual aims: optimising acetic acid concentration and identifying an effective corrosion inhibitor. A multifaceted methodology was employed, integrating weight-loss measurements, AC impedance and Polarisation curve analysis, SEM-EDS characterisation, orthogonal experimental design, and controlled-variable approaches. Key findings demonstrate that: (1) acetic acid inhibits corrosion of 110SS steel in hydrochloric acid, though the resultant corrosion rate exceeds acceptable industrial thresholds; (2) oleic acid imidazoline a ternary inhibitor comprising oleic acid imidazoline, cinnamaldehyde, and quaternary ammonium salt C14-GC exhibits synergistic corrosion inhibition in the mixed-acid system. This inhibitor can form a dense and homogeneous adsorbent film on 110SS steel surfaces, effectively suppressing anodic corrosion. Orthogonal experiments predicted that at 363.15 K, the corrosion inhibitor could achieve a maximum corrosion inhibition efficiency of 98.31% for 110SS steel in a 9% HCl + 9% HAc system, with a minimum corrosion rate of 4.96 g/(m 2 ·h). This work provides theoretical foundations for corrosion protection strategies targeting 110SS steel in the hydrochloric acid-acetic acid environments during carbonate matrix acidising.