Search results

The efficiency of some 2‐heterocarboxaldehyde‐2′‐pyridyl‐hydrazones as inhibitors for the acid dissolution of Al was studied by mass loss, hydrogen evolution and polarization measurement techniques. The corrosion rate was measured in 2M HCI at different temperature and concentrations; maximum percentage protection (85%) was obtained at 103M for the compound containing oxygen atom. The activation energies were calculated for all the additives used. The rate constant decreases as the inhibition efficiency increases. The results show that the studied materials influencing both the cathodic and anodic process. The mechanism of inhibition was proposed on the basis of the formation of a protective monolayer by the inhibitors molecules on the metal surface according to Langmuir isotherm.

Corrosion inhibitors are widely used in industry, although in many cases their surface chemistry is not well understood. Several nitrogen‐containing organic compounds have been used as corrosion inhibitors. Corrosion inhibition is a surface process which involves the specific adsorption of inhibitors on the metal surface. The extent of inhibition of metallic corrosion may depend on the nature of the metal surface and extent of adsorption of the inhibitor. The type of interaction of the inhibitor on the metal surface during corrosion has been deduced from its adsorption characteristics.

Cations such as Cu2+, Co2+, Ni2+, Zn2+ or Ba2+ increases the corrosion rate of aluminium in 2 mol.L−1 HCI. This corrosion rate could be decreased by the addition of inhibitors which may form complexes with the cation used. Measurements of the corrosion rate of aluminium in 2 mol.L−1 HCI with and without addition of aliphatic substituted P‐hydroxy acetophenone hydrazone derivatives (10−4 — 10−5 mol.L−1) has been studied by weight loss and galvanostatic polarization methods. The same inhibition efficiency of the compounds has been found using either of the methods. In general, the efficiency of the inhibitors increases with an increase in aliphatic chain length. Activation energies in the presence and in the absence of inhibitors has been evaluated. Galvanostatic polarization data indicate that all these compounds are predominantly cathodic inhibitors. The rate of corrosion increases with increase in temperature together with a decrease in protection efficiency indicating that inhibition occurs through adsorption of the additives.