Avaliação da formação de áreas não passivadas em tanques reservatórios de leite por soldagem elétrodo revestido”

Abstract

In the process of manufacturing both pasteurized and in natura milk storage tanks, the process of joining welded alloys is present, especially in regions where dirt accumulation may occur due to process defects and discontinuities. In addition, the heat input generated by the welding process can cause and generate non-passivated areas in the weld region. These characteristic areas show regions where there was no passivation of stainless steel, ie where the passive layer of chromium was not able to regenerate and protect the steel from traditional corrosion processes and even from microbiologically induced corrosion (MIC). In manual welding processes both for manufacturing and for repairing tanks this problem may be even greater, since the control of the electric arc and the supply of heat will depend on the skill of the welder in question. In this work, weld beads were made using the coated electrode deposited in plates of stainless steel 304 with a thickness of approximately 1.8mm. The areas of deposited material and thermally affected areas (ZTA or ZAC) are directly affected by the deposition and deposition of molten material, thus higher energy inputs produced larger non-passivated areas, thus losing the effect of the protection of the oxide layer. This increase of non-passivated area still presents a second problem, since without protection of the protective layer, the region is exposed to a greater microbial adhesion, facilitating the development of a differential aeration cell under the formed biofilm. This action directly favors the formation of Pitting Corrosion (PIT) which are considered to be powerful voltage concentrators.