Corrosion of aluminium in perchloric acid in presence of various inorganic additives

Abstract

The corrosion of aluminium in 1M HClO 4 at 40°C has been investigated using the potentiodynamic polarisation technique. The effect of various inorganic additives has been investigated. It was found that NO 3 , NO 2 and SCN anions exhibit an inhibiting action on acid corrosion of aluminium by reducing the general corrosion rate as well as raising the pitting potential E p . It was found that CrO 2 4 ions were unique in demonstrating a remarkably high inhibiting action but their in uence on the pitting potential was less pronounced than that of the group above. On the other hand, added halides induced an accelerating effect on the corrosion rate and lowered the pitting potential. However, SO 2 4 ions do not show any signi cant effect on the corrosion behaviour of Al in 1M HClO 4 . The results have been interpreted on the basis of the adsorption mechanism followed by incorporation into the native lm.

nionic Effect on the Acidic Corrosion of Aluminum and its Inhibition by Lupine Extract

“…1 represents the potentiodynamic polarization curves for aluminum in the three studied mineral acids at 30 ᵒ C. The polarization curves show Tafel behavior. In presence of HCl, the active region is followed by break down potential Eb; this behavior has been previously reported by several authors [13,14] and has been explained on the basis of the pitting corrosion of aluminum. The potentiodynamic polarization parameters for aluminum in different mineral acids at 30 ᵒ C are presented in Table 1.…”

“…It has been reported that the addition of Clions increases the anodic dissolution rate of aluminum either by incorporation of the Clion into the oxide film, by which additional charge carriers are generated [16], or by the participation of Clions in the metal dissolution reaction [17,18]. In our previous work [19], the action of Clions as an accelerator has been explained on the basis of ionic incorporation into a surface film which depends upon ionic size. Consequently Clions, by their small size, can be easily incorporated.…”

“…But the values of 1/y in case of Cland SO4 2ions indicate that each inhibitor molecule occupies more than one active site on aluminum surface. Since the efficiency of a given inhibitor is essentially a function of the magnitude of its binding constant K [19], the increase in the values of K in the presence of ClO4ions indicates better and stronger interaction of the inhibitor molecules with the metal surface in presence of perchlorate ions. This behavior can be discussed on the basis of the low coordination ability of the perchlorate ion which tends to make the active sites of aluminum surface free and ready to adsorb the inhibitor molecules.…”

Dry and wet lab analysis on benzofused heterocyclic compounds as effective corrosion inhibitors for mild steel in acidic medium

“…It has been reported that values of x > 1 imply the formation of multilayer of the inhibitor on the metal surface and x < 1 than one mean that the given inhibitor molecule will occupy more than one active site [43]. The efficiency of a given inhibitor is a function of the magnitude of binding constant k, large values of k indicate better and stronger interaction, whereas small values of k mean that the interaction between the inhibitor molecules and the metal is weaker [44]. Linear plots of Flory-Huggins isotherm and El-Awady kinetic model fitted with experimental data are depicted in Fig.…”

Electrochemical Corrosion Behavior of Aluminum in Perchloric Acid

“…A large number of investigations have been reported on adsorption of anions on aluminum corrosion and their inhibition or stimulation effects on aggressive acid media [7][8][9][10][11][12][13]. Recent study has been concerned with the effects of various inorganic additives, such as nitrate, nitrite, thiocyanate and chromate on the corrosion of aluminum in 1 M HClO 4 at 40˚C [14]. In the present work, potentiodynamic polarization technique was used to study the effect of different organic additives vis., acetate, citrate, benzoate, tetraethyl ammonium iodide and cyclam on the electrochemical corrosion behavior of aluminum in 1 M HClO 4 at 40˚C and their adsorption mechanism.…”