Study of Synergistic effect of diethylene triamine penta (methylene phosphonic acid) and adipic acid on the inhibition of corrosion of alkaline aluminium

The inhibition efficiency (IE) of diethylene triamine penta (methylene phosphonic acid) [DETAPMP] in controlling the corrosion of Aluminium metal in a medium containing 0.01M NaOH and Zn2+ions was studied by using weight loss measurements and electrochemical polarization studies. Similar investigations were carried out by adding the second inhibitor viz adipic acid (AA) also. The combined IE of the above two inhibitors was found to be more than 90%. All the synergism factor values (Sf ) calculated were greater than unity, confirming the synergistic effect of the two inhibitors. The protective film formed on the metal surface consists of Zn(OH)2 and complexes of Al3+ and Zn2+ with DETAPMP and AA. This is confirmed by UV – Visible spectra, FTIR Spectra and Atomic Force Microscopy (AFM). Surface morphology studies were done using scanning electron microscopy (SEM) and AFM. Both inhibitors act as mixed inhibitors and obey Langmuir adsorption isotherm

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