Fabrication and characterisation of porous, calcium enriched coatings on titanium after plasma electrolytic oxidation under DC regime

Abstract

The purpose of this work is to produce and characterize (chemical composition and roughness parameters) porous coatings enriched in calcium and phosphorus on the titanium (CP Titanium Grade 2) by plasma electrolytic oxidation. As an electrolyte, a mixture of phosphoric acid H 3 PO 4 and calcium nitrate Ca(NO 3 ) 2 ·4H 2 O was used. Based on obtained EDS and roughness results of PEO coatings, the effect of PEO voltages on the chemical composition and surface roughness of porous coatings was determined. With voltage increasing from 450 V to 650 V, the calcium in PEO coatings obtained in freshly prepared electrolyte was also found to increase. In addition, the Ca/P ratio increased linearly with voltage increasing according to the formula Ca/P = 0.035·U+0.176 (by wt%) and Ca/P = 0.03·U+0.13 (by at%). It was also noticed that the surface roughness increases with the voltage increasing, what is related to the change in coating porosity, i.e. the higher is the surface roughness, the bigger are pores sizes obtained.

Characterization of Porous Phosphate Coatings Enriched with Magnesium or Zinc on CP Titanium Grade 2 under DC Plasma Electrolytic Oxidation

“…To obtain the porous micro-coatings on titanium [34][35][36][37] and its alloys [38][39][40][41][42][43][44], plasma electrolytic oxidation (PEO) should be used. It is worth noting that the obtained porous coatings may contain elements originating from the electrolytes, which lead to a bone-like structure (phosphorus and calcium) [45][46][47] and show antibacterial properties (copper and zinc) [48][49][50][51][52][53][54] with simultaneous high corrosion resistance. It should be also pointed out that the addition of magnesium accelerates wound healing, what in case of biomaterials is very important.…”

“…It should be also pointed out that the addition of magnesium accelerates wound healing, what in case of biomaterials is very important. Additionally, it may be noted that the chemical composition [36,37,41,51] of PEO coatings as well as their porosity [42,52] which simply undergo the description by roughness parameters [55,56], may be expected.…”

Characterisation of porous coatings formed on titanium under AC plasma electrolytic oxidation

“…It addition, it should be noted that errors related to the voltage instability as well as with the distortion associated with the shape of the wave are also affected [30][31]. Porous coatings obtained by DC PEO processes with the use of concentrated phosphoric acid based electrolyte were described in previous papers [32][33][34][35][36][37].…”

Characterisation of porous coatings formed on titanium under DC plasma electrolytic oxidation

“…The PEO coatings are produced at DC and AC voltages of several hundred volts; in addition it should be noted that errors related to the voltage instability as well as with the distortion associated with the shape of the wave are also affected [30][31]. They are from obtained by DC PEO processes with the use of concentrated phosphoric acid based electrolyte in different conditions were described in previous papers [32][33][34][35][36][37]. The aim of this work is to present results of studies of DC PEO process with the use of electrolyte based on concentrated phosphoric acid H 3 PO 4 with the addition of copper nitrate trihydrate Cu(NO 2 ) 2 ꞏ3H 2 O to investigate effect of different voltages 500, 575 and 650 V DC on the obtained coatings physical and chemical properties.…”