Electrodeposition and characterization of hydroxyapatite coatings doped by Sr2+, Mg2+, Na+ and F- on 316L stainless steel

Abstract

Hydroxyapatite (HAp) co-doped by magnesium, strontium, sodium and fluorine was deposited on the 316L stainless steel (316LSS) substrates by electrodeposition method in electrolyte containing: Ca(NO3)2, NH4H2PO4, NaNO3, NaF, Sr(NO3)2 and Mg(NO3)2. The influences of scanning potential ranges and temperature on MgSrFNaHAp coatings were researched. The obtained coatings under the optimum condition of scanning potential range from 0 to -1.7 V/SCE, at 50 °C have single phase crystals of HAp, cylinder shape and the thickness of 8.9 μm. The tests of 316LSS, NaHAp/316LSS and MgSrFNaHAp/316LSS materials in physiological saline and simulated body fluid (SBF) solutions were carried out. The results showed that the dissolution of MgSrFNaHAp coatings was lower than that of NaHAp ones and open circuit potential (OCP) of MgSrFNaHAp/316LSS was higher than those of NaHAp/316LSS and 316LSS at any immersion time. After 21 immersion days, the impedance modulus of MgSrFNaHAp/316LSS reached 17.48 kxcm2, which was 4.2 and 1.7 times higher than those of 316LSS and NaHAp/316LSS, respectively. The corrosion current density (icorr) of MgSrFNaHAp/316LSS decreased about 2.3 and 7.8 times in comparison with that of NaHAp/316LSS and 316LSS, respectively. These results indicated that MgSrFNaHAp coatings can protect for the 316LSS substrates better than NaHAp coatings.