Erosion corrosion of Ti and Zr in acidic metastannic acid synthesis

Abstract

Abstract In synthesis of metastannic acid, erosion corrosion caused by strong acid and abrasion triggered by stannum granular both create a complex circumstance for reactor. Titanium and zirconium, as the major choices for fabricating the reactor, sustained the combined impact of corrosion and abrasion in the circumstance. While there are very few researches, focusing on the erosion corrosion of the reactor, in the synthesis of metastannic acid. The erosion corrosion behaviors of commercial reactor materials Ti (TA2) and Zr (Zr-1) were investigated in the acidic conditions (20 vol% H2SO4 or 20 vol% HNO3 solutions) according to the complex circumstance. Therefore the wear and corrosion properties were tested by weight loss method and electrochemical method separately, the corrosion situation, such as open circuit potential (OCP) and Tafel plot, of Ti and Zr were tested, the mass loss caused by corrosion and wear were quantitatively, and the surface morphology was observed by scanning electron microscope (SEM). Moreover the corrosion abrasion situation, OCP, Tafel plot, mass loss and surface morphology, had been investigated using self-made corrosion abrasion testing device too. The results showed that in the solution of 20 vol% HNO3, the corrosion rate of Zr increased by 120 times when the solution was heated to 200 °C under corrosion condition, and the corrosion rate of Ti increased by 8 times, indicating that the corrosion resistance of Zr is easier affected by temperature, the corrosion resistance of Zr is better than Ti. Under abrasion condition, using abrasion quartz sand particles as abrasion material, the mass loss rate of Ti and Zr was 159.23 mg/(m2·h) and 252.23 mg/(m2·h). Under erosion corrosion condition, the synergistic effect of erosion corrosion of Ti and Zr exacerbated the mass loss, their mass loss rate respectively was 788.05 mg/(m2·h) and 225.4 mg/(m2·h) especially in Ti-H2SO4 and Zr-HNO3 systems. A dense oxide layer detected on the surface of Ti and Zr, could improve the corrosion resistance, but it was easy to fatigue and peel off when there was abrasion material in the solution. A erosion corrosion model of Ti and Zr were established for serve life prediction, which could provide theoretical guidance for the design of reaction in production of metastannic acid.