Three novel di-quaternary ammonium salts as corrosion inhibitors for API X65 steel pipeline in acidic solution. Part I: Experimental results

• Three di-quaternary ammonium salts as corrosion inhibitors for carbon steel in 1 M HCl.
• The inhibition efficiency increased in the order of Schiff bases Q3 > Q2 > Q1.
• Surfactants acted as mixed type inhibitor and obeyed Langmuir adsorption isotherm.
• The addition of inhibitors enhanced Rct values while reduced Cdl values.
• Adsorption process is physical and exothermic accompanied by an increase in entropy.

Three novel di-quaternary ammonium salts were synthesized, characterized, and tested as corrosion inhibitors for API X65 steel pipeline in 1 M HCl. The inhibition effect of the prepared compounds was studied by EIS, Tafel polarization and weight loss measurements. Polarization curves revealed that the prepared compounds act as mixed type inhibitors. It was found that the inhibition efficiency increased with increasing the compound concentration and decreasing the temperature and also is dependent on the molecular structures. Adsorption of the prepared compounds on API X65 steel pipeline surface is a physical adsorption and obeys the Langmuir’s isotherm.

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