Resistance of Titanium to Sulfuric and Hydrochloric Acids Inhibited by Ferric and Cupric Ions

Abstract

Ferric and cupric ions are effective inhibitors for the corrosion of titanium in boiling 10 per cent sulfuric and boiling 10 per cent hydrochloric acids. The corrosion rates range from 3 to 55 mdd (0.001 to 0.012 ipy) for inhibitor concentrations from 0.03 to 0.005 M. Although the inhibitors are consumed as titanium corrodes, the consumption is moderate, particularly at the higher inhibitor concentrations corresponding to low corrosion rates. The primary mechanism, as indicated by potential measurements, is proposed as occurring through adsorption of Fe +++ or Cu ++ on the metal surface with accompanying satisfaction of surface valences and formation of a dipole layer with negative charge outward accounting for a noble potential.

Potentials of Iron, 18-8, and Titanium in Passivating Solutions

“…Similar inhibition is observed to hold for titanium (27,28), but with the difference that the beneficial effects extend to hydrochloric acid, unlike the situation for 18-8. It is of interest, therefore, to determine the parallel potential behavior of 18-8 and titanium in sulfuric acid as these inhibitors are added.…”

Passivity and Protection of Metals Against Corrosion

“…The noble metal ions have a similar beneficial effect on titanium in sulfuric as well as in hydrochloric acids. The favorable effect of Cu 2 + ions on the corrosion rate of titanium in hydrochloric acid was shown in reference [200]. In 5% HCI at 94°C, the corrosion rate of titanium is about 6.9mm/year.…”

“…Many experimenters [133,187,[197][198][199][200][201][202][203][204] have shown that the introduction of ions of noble metals, such as Pt, Hg, Cu, Ag, and Pd, into acid solutions can substantially improve the corrosion resistance of some metals and alloys. It can be seen from the data presented in Table 38 [197] that the addition of Hg, Cu, Ag, and Pt ions to a sulfuric acid solution produces an appreciable reduc- tion in corrosion rate of chromium-nickel and chromium-iron steels and of silicon cast iron.…”

“…The introduction of copper ions into the solution reduces the corrosion rate of titanium more than a thousandfold. (2) 10% H 2 SO, (test duration, 2 days), as a function of copper ion concentration in solution [200].…”

High Temperature Corrosion of Titanium Under Conditions Relevant to Pressure Leaching: Mass Loss and Electrochemistry

“…42 Considering the extremely high corrosion rate of Ti in 30 g L −1 H 2 SO 4 + 12 g L −1 Cl − solution at 150°C (as documented above), it was deemed necessary to perform long-term immersion experiments in the same 30 g L −1 H 2 SO 4 + 12 g L −1 Cl − solution, but also in the presence of Cu 2+ 43 According to these formulas, the Fe 3+ solubility in 30 g L −1 H 2 SO 4 solutions should be around 0.37 g L −1 at 150°C, which is lower than the Fe 3+ concentrations used in this work, i.e., 1 and 5 g L −1 . Later, Sasaki, et al, also reported that, at the same H 2 SO 4 concentration, the concentration of Fe 3+ ions decreased considerably with an increase in the addition of Na + ions, and the Fe 3+ ions precipitated as sodium jarosite.…”