Avaliação da corrosão do aço carbono ASTM A106 GR. B submetido a um meio rico em finos de processo de produção de liga ferro-níquel

Abstract

The ferro-nickel alloy, commonly referred to as FeNi, has 19% to 38% nickel in its composition and is of significant importance in the stainless-steel production, in addition to being used as a raw material for alloys with higher nickel contents. Its production by pyrometallurgical means occurs at elevated temperatures in submerged electric arc furnaces, in a carbothermic reduction process, which generates process gases with massive quantities of fine particles that need to be collected in gas cleaning system. In some plants, a corrosion process has been observed, to a greater or lesser extent, in the water-cooled ducts of this system, after a few years of operation. Therefore, the general objective of this work is to evaluate the corrosivity of the particles in ASTM A106 Gr. B carbon steel, the main construction material of this equipment. For this purpose, analyses of the chemical composition of the particulates were performed by X-ray fluorescence and energy dispersion spectroscopy, in addition to corrosion tests of carbon steel in the presence of this material by means of electrochemical polarization techniques and complemented by scanning electron microscopy tests, to evaluate the behavior of carbon steel regarding corrosion in the presence of this particulate. The results found show that the corrosivity of the dust is not significant for this steel, and it is not possible to draw a direct correlation between the degree of corrosion and the concentration of dust in the medium, however its presence and deposition are directly related to the corrosive process due to the formation of piles. These results were compared with data from field inspections and showed a correlation with characteristics and operating parameters of the equipment.