The inhibition of the corrosion of pure iron in 0.5 M sulphuric acid by n-alkyl quaternary ammonium iodides

n-butyl, n-dodecyl and n-hexadecyl ammonium iodides were prepared and potentiostatic polarization studies showed that each quaternary ammonium salt inhibits the corrosion of pure iron in 0.5 M sulphuric acid at 30°C. The behaviour is similar to the corresponding bromides and the polarization curves indicate that the compounds behave as mixed inhibitors. Each compound exhibits Langmuirian behaviour and inhibition increases with increasing alkyl chain length. This is attributed to cohesive Van der Waals' forces between the positive head groups co-adsorbed with iodide ions on the positively charged iron surface.