Abstract
Dodecyl pyridinium bromide (DDPB), tetradecyl pyridinium bromide (TDPB) and dodecyl 1,1′-bispyridinium dibromide (DDBPB) were successfully synthesized, characterized and evaluated for HCl pickling of X-60 low carbon steel. Order of corrosion inhibitions efficiencies, as revealed by both electrochemical and gravimetric studies, is TDPB > DDPB > DDBPB. The degree of hydrophilicity of inhibitors as predicted by a partition coefficient (Log P) and supported by a contact angle measurement was found to be responsible for their order of corrosion inhibition efficiencies. Adsorption of DDPB, TDPB, and DDBPB through the pyridinium nitrogen on mild steel surface was confirmed by ATR-FTIR and SEM-EDX analyses. The pyridinium nitrogen was found not to be the only factor responsible for their efficiency, but hydrophobes and the orientation of the hydrophilic ring were responsible, which incline to the deviation of experimental results and the order of Monte Carlo simulation adsorption energies. DDPB, TDPB, and DDBPB obey the Langmuir isotherm model despite major contributions of the film formed on the surface of X-60 mild steel on their overall inhibition corrosion resistance.
Highlights
Effective elongation, high yield and tensile strength properties of X-60 low carbon steel (X-60 mild steel) as one of the API 5L grade X mild steel have made it a suitable metallic material in various offshore and onshore applications
NMR, 13 C NMR and FTIR spectra obtained for dodecyl pyridinium bromide (DDPB), tetradecyl pyridinium bromide (TDPB) and DDBPB are presented as Figures S1–S3, respectively
DDPB (1): The onset of thermal decomposition: the color change to brown at 152.4 ◦ C, indicating the melting point of DDPB
Summary
High yield and tensile strength properties of X-60 low carbon steel (X-60 mild steel) as one of the API 5L grade X mild steel have made it a suitable metallic material in various offshore and onshore applications. These attractive mechanical properties, as well as its low cost compared to other alternative materials, have been a major consideration for its enormous applications despite poor resistance to corrosion in different environments [1,2,3,4,5]. Hydrochloric acid (HCl) pickling is preferred to other inorganic acids (hydrofluoric, sulfuric, phosphoric and nitric acids) pickling in steel mills and other steel applications industries due to its high regeneration, less pickling time, minimal loss of substrates, lower temperature and high-quality finished products [6,7].
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