This study proposed a novel thermochemical activation (TCA)
method to modify the surface of 316L stainless steel (SS).
At the first stage, phosphate ions were introduced to 316L
SS surface by a heat-diffusion process. After rapid quenching
into calcium citrate solution, calcium and hydroxide ions
were sealed in the TCA compound layer. The TCA and original
316L SS were immersed in Hanks’ solution to evaluate
their biocompatibility. Electrochemical impedance spectroscopy
analysis showed that the surface active compound
layer affected the TCA 316L SS, and its total impedances of
Bode and Nyquist plots were higher than that of the original
ones during immersed in Hank’s from 1 to 14 days. After TCA
treatment, the corrosion resistance increased greatly, and
thus reducing the release of ions from stainless steel, such as
Fe, Cr, Ni and Mo. In the Ca- and P-rich areas, the ions were
guided to deposit in the Hanks’ solution, forming bone-like
hydroxyl apatite. The treatment has been proven to reduce
the ionic release from 316L SS, which is considered to be a
great improvement for implanted alloys.
