Evaluation of Cupronickel Alloy Used in Sodium Chloride Solutions Contaminated with Nitrogenated Fertilizers

Cupronickel alloys have been used in the manufacture of equipment, pumps and pipes for refrigeration systems and heat exchangers, among other applications. Certain nitrogen fertilizer plants are built near seaports for the transport of products, and use seawater for refrigeration systems. However, in the case of accidental discharge, it is important that seawater capture does not cause damage to materials and equipment, preserving the integrity and guaranteeing the service life of the equipment. The present work analyses the behavior of cupronickel 90/10 alloy (Cu with 10 wt. % Ni) in relation to corrosion, through the development of gravimetric (mass loss) and electrochemical tests in solutions of 3.5 wt. % sodium chloride, with the additions of nitrogen fertilizer in several proportions. A superficial attack was observed on the surfaces of the alloy specimens, and the presence of pits was not observed. In addition, a greenish coloration on the surface developed with increased immersion time and with the greatest addition of fertilizer. The results of the mass loss tests of the cupronickel alloy with saline solution showed that for nitrogen fertilizer injection, in concentrations of 1, 3 and 5 wt. %, the corrosivity varies from low to moderate, and that despite suffering corrosion in the saline environment, cupronickel has a good resistance to this corrosive process, and can be considered the most suitable material for application in highly aggressive environments, such as in the sea water capture system.