Experimental evaluation of quinolinium and isoquinolinium derivatives as corrosion inhibitors of mild steel in 0.5 M H2SO^sub 4^ solution

The 1-methylquinolinium iodide (I) Qui+, I- and 2-methylisoquinolinium iodide isoQui+, I- were investigated as a corrosion inhibitors for mild steel in sulfuric acid using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The results indicated that the corrosion inhibition efficiency and extent of surface coverage were increased with increase in inhibitors concentrations. Polarization curves revealed that both inhibitors acted as a mixed-type inhibitor. The thermodynamic parameters were evaluated for corrosion inhibition process. The adsorption of both inhibitors on mild steel surface obeyed Langmuir adsorption isotherm.