A comparison between corrosion performances of titanium grade 2 and 7 in strong reducing acids

Abstract

Titanium has a good corrosion resistance, owing to a thin, compact oxide layer that is formed spontaneously when the metal is exposed to the environment. However, even titanium can be subject to corrosion, for example, when exposed to reducing strong acids. This paper aims to analyze the differences in corrosion resistance of commercially pure titanium (Ti grade 2) and the most resistant Ti-Pd alloy (Ti grade 7, ∼0.2% Pd) in a strong reducing acid environment. Immersion tests, with results collected in the form of corrosion rates, are provided in the first part of the present work. Corrosion morphology is investigated using optical microscopy and laser profilometry. Then, an electrochemical characterization of both metals has been performed by means of cathodic polarization tests, electrochemical impedance spectroscopy, and linear polarization resistance. Weight loss data, electrochemical tests, and corrosion morphology are in good agreement: H 2 SO 4 , HCl, and oxalic acid are the most aggressive chemicals for commercially pure titanium. In such conditions, the use of Ti grade 7 appears mandatory.

Sealing of porous titanium oxides produced by plasma electrolytic oxidation

“…Being the solubility of calcium hydroxide in water an exothermic process, its stability can be enhanced in service conditions, exploiting relatively high temperatures, thereby making the sealing procedure more efficient. In particular, knowing the high aggressivity of hot concentrated sulfuric acid on grade 2 titanium [11,12] inducing corrosion rates of several mm/year even in presence of anodic coatings [13] the reaction between Ca(OH) 2 and H 2 SO 4 can favor the formation of a calcium sulfates skin. Depending on its uniformity and formation kinetics the reaction between the Ca(OH) 2 deposits and the acidic environment can be eventually stopped.…”

Features of Microstructural Evolution and Corrosion Behavior of Ti6Al4V Titanium Alloy Fabricated from Elemental Powder Blends

“…The corrosion resistance of the sintered titanium was investigated in 40 wt.% H2SO4 acid by the potentiodynamic polarization and static immersion tests at a room temperature (20°C). This sulfuric acid concentration was chosen because, according to previous studies [15][16][17]20], the most intensive dissolution of titanium occurs at this 40 wt.% concentration. Therefore, hard conditions of corrosion tests were chosen, which would allow us to more qualitatively evaluate the mechanisms of corrosion processes and the prospects for the use of the investigated titanium alloys.…”

An Investigation into the Effect of Electro-Contact Heating in the Machining of Low-Rigidity Thin-Walled Micro-Machine Parts

“…The accuracy class of electrical devices can be increased by using high-quality materials that ensure minimum distortion of electro-magnetic characteristics. For this reason, thin-walled casings of electric micro-machines are produced from Grade 2 and Ti-64 titanium alloys [ 23 , 24 ]. Increased demands are also placed on the accuracy of the manufacture of similar parts and the stability of the dimensions of a part a long time after it has been machined [ 25 ].…”