Hafnium surface changes during dissolution in concentrated sulfuric acid

Abstract Scientific studies involving hafnium have grown significantly in recent years due to the potential applications that this metal has. These potential applications come from the properties of this element, which for many years since its discovery were neglected in research. Among the factors that contributed to this was the high cost of extracting its ores from nature. One of the properties is the solubility of this metal in concentrated sulfuric acid, reacting to form hafnium(IV) sulfate and hydrogen gas. This acid is one of the few that can dissolve this metal, since hafnium is highly resistant to corrosion. The present work reports a chemometrically planned study on the surface of hafnium metal during its dissolution in sulfuric acid at different temperatures (13 °C, 25 °C and 97 °C) and for different times (5 minutes, 60 minutes and 120 minutes). Samples of metallic hafnium were completely immersed in sulfuric acid, subsequently characterized by scanning electron microscopy and the mass variation of the samples was analyzed. The corrosion of hafnium occurs only after the rupture of the protective film of hafnium(IV) oxide of the material, this rupture being faster as the temperature increases.