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Due to the constituent nitrogen atom of the amino group, amines have been extensively used as inhibitors of metallic corrosion. This article reviews the reported uses of aniline and related aromatic amines as corrosion inhibitors.

COPPER is by far the most important non‐ferrous metal used in industry. By virtue of its valuable physical and mechanical properties, long life, comparative cheapness and high scrap value, it occupies a position next only to iron and steel in commercial importance.

This concluding part reviews the actions of inhibitors to acidic, ammonical, organic, atmospheric and miscellaneous product corrosion on aluminium. The comprehensive reference list is also concluded.

The discovery of the Hall‐Herqult process for the manufacture of aluminium made it possible to obtain the metal in large quantities. Soon it attained the position of a major industrial metal due to its lightness combined with strength, capacity to take up a high polish, excellent conductivity of heat and electricity. Moreover it gives a wide range of extremely valuable alloys with diverse elements such as copper, magnesium, nickel, silicon, zinc, etc.

A survey of technical literature indicates that there is a shortage of excellent corrosion inhibitors for zinc in non‐oxidizing acids, particularly sulphuric acid. This paper aims to describe the behaviour of ethylenediamine‐N‐N′‐dibenzylidene, ethylenediamine‐N‐N′‐disalicylidene, ethylenediamine‐N‐N′‐dicinnamylidene, triethylenetetramine tribenzylidene and triethylenetetramine trisalicylidene as corrosion inhibitors for zinc in sulphuric acid solutions. The objective of this research work also is to have an insight into the action mechanism of these inhibitors.

The effect of the various parameters affecting the action of the above‐mentioned corrosion inhibitors has been studied using weight‐loss data and polarisation measurements. Adsorption data also were utilized.

The inhibitors showed excellent corrosion inhibition (>99 per cent) at effective inhibitor concentrations. The two salicylidenes were better corrosion inhibitors than were corresponding benzylidenes. It appeared from this study that an efficient inhibitor is characterised by a relatively greater decrease in free energy of adsorption, lower entropy of adsorption and relatively lower heat of adsorption. Basically, these inhibitors were cathodic, as was revealed by polarisation data, and the inhibitors followed Langmuir adsorption isotherm behaviour. In general, the conjoint action of the inhibitor and the cathodic current was synergistic.

Powerful Schiff bases still need to be synthesized so as to be effective at extremely low concentrations. The behaviour with other metals and alloys in diverse media also requires to be investigated.

Very few inhibitors demonstrate such excellent corrosion inhibition of zinc in aggressive corrosive media. Such detailed investigations on corrosion inhibitors are unusual.

α‐naphthylamine, thioglycolic acid and urea have been investigated as inhibitors of the corrosion of 63/37 brass in nitric acid. Thioglycolic acid is the most efficient inhibitor which affords nearly complete protection to brass. All the three substances predominantly act on local cathodic areas.

The evaluation of Schiff bases derived from o‐, m‐ and p‐aminophenols and salicylaldehyde as corrosion inhibitors of zinc in sulfuric acid and to study their action mechanism.

The effect of various parameters on the behaviour of these inhibitors has been studied using the weight loss and polarization measurements.

In general, the ortho isomer was highly effective as a corrosion inhibitor because it formed a chelate with a six‐membered ring and moreover the ortho isomer possessed pronounced electromeric effect. These inhibitors obey the Langmuir adsorption isotherm. The almost constant performance with temperature in the case of ortho and para isomers in 0.5 M sulfuric acid suggested strong adsorption bonds. The thermodynamic parameters suggested that this strong interaction of the inhibitor molecules with the metal surface resulted in spontaneous adsorption. It may be concluded that a good inhibitor is characterised by a relatively greater decrease in free energy of adsorption, lower entropy of adsorption and higher heat of adsorption. Polarization data indicated that all these isomers were predominantly cathodic inhibitors. The conjoint effect of external cathodic current and these inhibitors was either synergistic or additive.

Even more powerful Schiff bases need to be synthesised and evaluated as corrosion inhibitors with a number of metals and alloys in diverse media, which may be effective at low concentrations.

Very few inhibitors exhibit such excellent inhibitive effect on zinc in aggressive corrosive media. Rarely do we find such detailed studies.

Mann, Antonucci, Nathan, Hackerman and Antropov investigated aniline and N — substituted methyl and ethylamines as corrosion inhibitors for iron in acidic media. The present study was therefore undertaken to investigate the retardation of corrosion of aluminium 65S in hydrochloric acid.

The present paper deals with chloroanilines and anisidines as corrosion inhibitors for aluminium‐3S in hydrochloric acid solutions. Some of these compounds have previously been investigated as corrosion inhibitors for aluminium‐2S1 57S2 and 65S3 in hydraulic acid. However, it is well known that the behaviour of inhibitors changes with the metal or even with a change in the composition of the alloy.

2: Aminobenzoic acids as inhibitors in nitric acid Ortho, meta and para aminobenzoic acids have been studied as corrosion inhibitors for 60/40 brass in nitric acid. Ortho and para aminobenzoic acids are cathodic in action whereas meta aminobenzoic acid acts by influencing both the cathodic and anodic reactions.