Novel macrocyclic cationic surfactants: Synthesis, experimental and theoretical studies of their corrosion inhibition activity for carbon steel and their antimicrobial activities

[Display omitted] •Mannich base was easily transformed into novel mono & gemini cationic surfactants.•icorr reduces &Ecorr changes marginally by the adding of surfactants in 5 %HCl.•Rct performance of DHNBMBDMB is greater than DHNMMB owing to adsorption centers.•Theoretical discussions are compatible with laboratory corrosion assessment studies.•SEM & AFM techniques established the formation of a protective layer on CS surface. Morpholinomethylnaphthalene-1-ol (MMN-OH) and 2, 6-Bismorpholinomethyl naphthalene-1, 5-diol (BMND-OH) were synthesized via Mannich reaction. The novel monomeric cationic surfactant (DHNMMB) and gemini cationic surfactant (DHNBMBDMB) were obtained based on the previous Mannich compounds through quaternization reaction. The resulting structures confirmed by IR, 1HNMR, and mass spectroscopies. Gravimetric and electrochemical techniques were utilized to assess the inhibitory activity of the synthesized surfactants on CS deterioration in 5% HCl. We note that DHNBMBDMB is better than DHNMMB. This is due to the chemical structure and surface properties. The maximum inhibition performance of DHNBMBDMB and DHNMMB at 2.5 × 10−3 M is 96.14 and 94.65%, respectively. Tafel curves indicated that the DHNMMB and DHNBMBDMB were hybrid-type inhibitors. Adsorption of DHNMMB and DHNBMBDMB onto CS surface obey Langmuir model. Both DFT and MC simulation studies ofDHNMMB and DHNBMBDMB compounds are discussed thoroughly and agree with the laboratory experimental corrosion tests. SEM & AFM photos show a good CS surface in the presence of DHNMMB andDHNBMBDMB versus the absence of them. The antimicrobial activities of all the synthesized Mannich bases and their surfactants were tested. The surfactants had a talented effect against Candida albicans.