The Evaluation of Certain Organic Nitrogen Compounds As Corrosion Inhibitors★

Abstract

Abstract The Static Water Drop Test adapted to research methods has been utilized to evaluate the corrosion inhibiting ability of a number of heterocyclic nitrogen compounds. Most of these heterocyclic N derivatives were synthesized and purified and evaluated in a petroleum-type lubricating oil and a synthetic diester-type lubricating oil. The effect of various functional groups and their positions in the molecule was related to the corrosion inhibiting properties. It was found that the adsorptive power was a function of the heterocyclic nitrogen containing a hydrogen atom as the substituent. It was also found that the adsorptive power at the heterocyclic nitrogen atom was lost when other substituents replaced the hydrogen. It was concluded that the adsorptive effect of the heterocyclic nitrogen is due to its unshared electron pair, which is sterically hindered when substituents other than hydrogen are attached. N-Hydroxyalkyl derivatives in diester oil seemed to arrange themselves in order of effectiveness on the basis of the position of the hydroxyl group in the alkyl chain. The closer the hydroxyl was to the heterocyclic nitrogen the more effective it was as a corrosion inhibitor. There was no way to explain the order of effectiveness of the same compounds in petroleum oil. 5.8.1