Studies on the inhibitory effect of different surfactants on ammonium chloride corrosion

Abstract

Corrosion of heat exchangers by ammonium chloride (NH4Cl) is a common occurrence in the refineries. A variety of methods have been adopted to prolong the service life of equipment in such circumstances, such as the use of various additives such as surfactants or by washing with water. In this paper, a series of experiments are performed to investigate the effects of different surfactants (cationic, anionic, amphoteric, and nonionic) on NH4Cl corrosion using the sessile drop technique and electrochemical measurements. The results show that the presence of a surfactant can increase the wettability of an NH4Cl solution, decreasing the contact angle between the solution and a test material. The surface tension of an NH4Cl solution containing an anionic surfactant is the lowest, but the self-corrosion potential of such a solution is the greatest. The addition of a cationic surfactant has no inhibitory effect on corrosion, and indeed increases the corrosion rate. However, with a nonionic surfactant, it is possible to significantly decrease the corrosion rate of an NH4Cl solution, although the inhibitory effect decreases with increasing temperature.