ANODIC DISSOLUTION OF TITANIUM IN SULFURIC ACID BROMIDE SOLUTIONS

Аннотация

Titanium is inert in many different oxidizing environments, prone to passivation. The metal is
chemically insoluble in acids, resistant to corrosion and environmental impacts. In the present work, the dissolution
behavior of titanium electrode in the sulfuric acid bromide solution under anodic polarization was shown for the first
time and laws of the process were determined. The effect of the anode current density (200-1200 A/m2
), potassium
bromide solution (1.0-5.0 M) and sulfuric acid concentration (0.5-2.5 M), solution temperature (25-80 ˚С) and
electrolysis duration (0.5-2 hours) on the current output of titanium dissolution were considered. With an increase the
current density at the anodic polarized titanium electrode from 200 A/m2
to 600 A/m2
, the current output (CO) of
titanium dissolution increases, and at higher current densities, a decrease in CO of titanium dissolution is observed
due to the appearance of an oxide coating on titanium surface. The influence of the Br–
ion concentration and the
sulfuric acid concentration was studied separately with the aim of systematically studying the effect of the electrolyte
nature on the dissolution of titanium. With an increase of the bromide ions concentration, poorly soluble bromide
compounds are formed, which leads to a decrease in the CO of the anodic dissolution of titanium. An increase in the
concentration of sulfuric acid, i.e. the concentration of hydrogen ions contributes to the dissolution of titanium, the
CO of the anodic dissolution of titanium increases. A 1.5 times increase in the CO of titanium was observed upon
acidification of an aqueous electrolyte containing Br-
ions with 0.5 M sulfuric acid and an increase in the
concentration of bromide ions. However, with an increase in the concentration of sulfuric acid in the bromide
solution, the CO of the anodic dissolution of titanium increased significantly and reached 70%. The CO of titanium
dissolution has a maximum value in a 2.5 M solution of sulfuric acid and in a 1.0 M solution of potassium bromide.
The reaction order of the electrode process during electrolysis with sulfuric acid was calculated and it was shown that
the reaction proceeds under diffuse conditions. An increase in the duration of electrolysis leads to concentration
polarization due to the accumulation of electrolysis products on the electrode surface and slows down the
electrochemical dissolution of titanium. The CO of the dissolution of the titanium electrode abnormally decreases
with increasing temperature of the electrolyte. The influence of the basic electrochemical parameters on the
dissolution of the titanium anode was studied and the optimal conditions for its dissolution were established. It was
found that under optimal electrolysis conditions, the current output of dissolution of titanium has a value of more
than 70%