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Recent Advances On The Influence Of Microstructural Characteristics On Corrosion Resistance In H2SO4 Of Anodized Titanium

Industrial usage of Plasma Electrolytic Oxidation (PEO) has grown consistently in recent years, thanks to the improved characteristics imparted to the oxide film in terms of surface adhesion, hardness, crystallinity, uniformity, and corrosion resistance. The metallic substrate is not subjected to elevated temperature and the overall equipment complexity is relatively simple, making the technique a good candidate for surface functionalization. In PEO treatments, high voltages are employed (~ 150-750 V 1) allowing for the formation of an insulating, or at least semiconductive, oxide layer that’s limits ion transport responsible for the initial coating growth. Beyond the spark voltage (prerequisite the enter the PEO regime) oxidation does not occur only as the result of a continuous flow of ions but rather it takes place after the cooling of a plasma discharge.

Product Number: 51322-17589-SG
Author: Luca Casanova, MariaPia Pedeferri, Gianluigi A. Botton, Marco Ormellese
Publication Date: 2022
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Commercially pure titanium has been anodized with the use of a pulsed signal in unipolar regime, with 25 % of anodic contribution at low frequency (20 Hz). This anodizing regime can effectively enhance thickness and crystallinity of the barrier region directly in contact with the metallic substrate. The latter condition will be particularly advantageous for corrosion resistance enhancement in strong reducing acidic environment, as concentrated hot sulfuric acid (10 %v/v at 60 °C). Corrosion response has been investigated through the use of Electrochemical Impedance Spectroscopy (EIS) and results compared with weight-loss tests and Linear Polarization Resistance (LPR). The higher degree of crystallinity of the coating, in the interfacial region, will be found to provide an effective barrier against proton diffusion thus retarding debonding of the oxide promoted by hydrogen evolution reaction (HER).

Commercially pure titanium has been anodized with the use of a pulsed signal in unipolar regime, with 25 % of anodic contribution at low frequency (20 Hz). This anodizing regime can effectively enhance thickness and crystallinity of the barrier region directly in contact with the metallic substrate. The latter condition will be particularly advantageous for corrosion resistance enhancement in strong reducing acidic environment, as concentrated hot sulfuric acid (10 %v/v at 60 °C). Corrosion response has been investigated through the use of Electrochemical Impedance Spectroscopy (EIS) and results compared with weight-loss tests and Linear Polarization Resistance (LPR). The higher degree of crystallinity of the coating, in the interfacial region, will be found to provide an effective barrier against proton diffusion thus retarding debonding of the oxide promoted by hydrogen evolution reaction (HER).

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