Surface Modification of Iron Substrates by Ti⁺-O⁺ Double-ion Implantation -Coloring and Corrosion Inhibition

Abstract

Oxidation of titanium by additional O⁺-implantation and electrochemical properties of the Ti⁺-O⁺ implanted iron were studied for coloring and corrosion inhibition of an iron surface. The double-ion implantation with Ti⁺ and O⁺ in iron substrates was carried out with doses of 3×10¹⁶×10¹⁶, and 1×10¹⁷ Ti⁺/cm2 at 150 keV, and with 1×10¹⁶-2×10¹⁷O⁺/cm2 at 35 and 50 keV by means of a RIKEN 200 kV Low Current Implanter. Concentration-depth profiles of Ti were measured by secondary ion mass spectroscopy (SIMS). The profiles of Ti showed gaussian-like distribution which are predicted by the corrected LSS theory with sputtering effect. The oxidation state of the Ti in the surface layer were measured by X-ray photoelectron spectroscopy (XPS). The Ti is metallic in Ti⁺-implanted iron and TiO² is buried in the Ti⁺-O⁺ double-ion implanted iron. The anodic dissolution behaviour of the ionimplanted iron electrodes was studied by a cyclic voltammetry in acetate buffer solution of pH 5. The dissolution properties were related to the oxidation states of Ti and colors appeared with electrochemical oxidation. Depression of the anodic dissolution without coloring was seen for the Ti-implanted iron with the additional 1×10¹⁶ O⁺/cm2 implantation. Whereas, the color appeared after the anodic oxidation for the implanted iron with the oxygen closes higher than 1×10¹⁷ O⁺/cm2. implantation. Whereas, the color appeared after the anodic oxidation for the implanted iron with the oxygen closes higher than 1×10¹⁷ O⁺/cm2. The mechanism of the coloring has been explained by enrichment of Ti in the surface layer caused by the selective dissolution of iron from the Ti⁺-O⁺ im-planted iron surface. We concluded that the double-ion implantation will be applicable to the surface modification in order to achieve the coloring of iron surface as well as to inhibit the corrosion of iron.