Characterisation of anodic oxide films on zirconium formed in sulphuric acid: XPS and corrosion resistance investigations

Abstract

Present work describes investigations of a two-step process consisting of galvanostatic anodising in a 1 M H 2 SO 4 solution at 100 mA cm −2 up to the limiting voltages of 20, 60, 80, 100 and 120 V, directly after which potentiostatic regime was employed and the current was allowed to drop. The total treatment time (5 min) was held constant for all samples. The treatment was carried out to improve the corrosion resistance of zirconium in physiological conditions, which was determined by electrochemical evaluation in Ringer's solution. XPS studies revealed that after anodising sulphur was incorporated into the oxide film in the form of sulphated zirconia. The maximum content of sulphate in the oxide layer was observed after anodising at 80 V. Anodising at higher voltages resulted in formation of coatings with decreasing amount of sulphur. It was found that there is a strong correlation between the sulphur content in the oxide layers and the measured corrosion current density. On the other hand, the pitting corrosion resistance seemed to be unaffected by the presence of S and it was improving with the increasing limiting voltage of the treatment.

Characterization of Porous Phosphate Coatings Enriched with Calcium, Magnesium, Zinc and Copper Created on CP Titanium Grade 2 by Plasma Electrolytic Oxidation

“…sodium silicate (Na 2 SiO 3 ) with trisodium phosphate (Na 3 PO 4 ), and sodium aluminate (NaAlO 2 ) [5] calcium hypophosphite Ca(H 2 PO 2 ) 2 with phosphoric acid H 3 PO 4 [9] sodium phosphate monobasic monohydrate (NaH 2 PO 4 ·H 2 O) with calcium acetate hydrate (Ca(CH 3 COO) 2 ·H 2 O) and strontium hydroxide 8-hydrate (Sr(OH) 2 ·8H 2 O) [18] calcium acetate Ca(CH 3 COO) 2 2H 2 O, and Na 2 SiO 3 , ethylenediaminetetraacetic acid (EDTA), and sodium hydroxide NaOH [19] tri-sodium orthophosphate (Na 3 PO 4 ·12H 2 O) with potassium hydroxide (KOH) and di-sodium tetra borate (Na 2 B 4 O 7 ·10H 2 O), and trisodium citrate dihydrate (C 6 H 5 Na 3 O 7 ·2H 2 O), and sodium meta silicate nonahydrate (Na 2 SiO 3 ·9H2O) [20] disodium phosphate (Na 2 HPO 4 ) [21] ammonium sulfate solution ((NH 4 ) 2 SO 4 ) [22] sodium dihydrogen phosphate (NaH 2 PO 4 ) with calcium acetate (Ca(CH 3 COO) 2 ) and strontium(II) acetate (Sr(CH 3 COO) 2 ) [23] sodium hydroxide (NaOH) with sodium phytate (Na 12 Phy) [24] sodium phosphate heptahydrate (Na 2 HPO 4 ·7H 2 O), with α-Al 2 O 3 and ketoconazole [25] trisodium phosphate (Na 3 PO 4 ) with hydrated sodium borate (Na 2 B 4 O 7 ), and sodium tungstate (Na 2 WO 4) [26] ethylenediaminetetraacetic acid (EDTA) with calcium (Ca(CH 3 COO) 2 ), Ca(H 2 PO 4 ) 2 , sodium hydroxide (NaOH) [27] It should be pointed out that, in the majority of the literature, the presence of titanium oxides in PEO coatings obtained on titanium in aqueous solutions is most often reported. However, Sowa et.…”

“…The electrochemical treatment which is known in the literature as Plasma Electrolytic Oxidation (PEO), Micro Arc Oxidation (MAO), or Spark Discharge Anodizing (SDA) may be used to form micro-porous coatings on lightweight metals, such as titanium [1], zirconium [2], tantalum [3], niobium [4], and titanium alloys (Ti6Al4V [5], Ti6Al7Nb [6], Ti-Nb-Zr-Sn [7], NiTi [8], Ti13Nb13Zr [9].…”

Characterization of Porous Phosphate Coatings Created on CP Titanium Grade 2 Enriched with Calcium, Magnesium, Zinc and Copper by Plasma Electrolytic Oxidation

“…Standard electropolishing [1][2][3][4], magnetoelectropolishing [5][6][7] as well as high-current-density electropolishing [8][9][10] may be used to improve nano-scale chemical [11][12][13], and corrosion [3,6,14] properties of materials, as well as their surface roughness [3,[15][16] and biocompatibility [17][18]. The other electrochemical treatment, known in the literature under the names of Plasma Electrolytic Oxidation (PEO) or Micro Arc Oxidation (MAO) or Spark Discharge Anodizing (SDA), may be used to form micro-porous coatings on lightweight metals, such as titanium [19][20][21], zirconium [22], tantalum [23], niobium [24] and their alloys (Ti6Al4V [25][26], Ti6Al7Nb [27], Ti-Nb-Zr [28], Ti-Nb-Zr-Sn [29], TNZ [30], NiTi [31]). The porous coatings obtained with such method are mostly used as biomaterials and are enriched with calcium and phosphorus to form structure similar to hydroxyapatite [33][34][35] with the addition of bactericidal zinc [36] and copper [37][38], as well as magnesium [36], which is added in case of acceleration of wound healing.…”

Comparative investigations of structure and properties of micro-arc wollastonite-calcium phosphate coatings on titanium and zirconium-niobium alloy

“…MAO modification of Ti, Mg, and their alloys has been extensively investigated [4] , [5] , [9] , whereas studies of MAO modification of Zr and its alloys are still quite limited [6] , [10] , [11] , [12] . It was demonstrated by Ref.…”

“…It was demonstrated by Ref. [11] , that depending on the anodic oxidation conditions for deposition of oxide coatings on Zr, i.e. voltage, current density, electrolyte composition and temperature, it is possible to grow of oxide layers with thickness of several hundred nanometers.…”