Ti alloys are commonly employed for making bone plates (Fadli et al. 2019).

However, the use of metals becomes limited due to their poor biocompatibility

with their hosts as well as limited organ function and influence on the bioactivity

in the body. Metals also cannot regenerate new bone. In addition, when interacting

with the host tissue, the corrosion products of the metals cause severe infection and

implant failure. Biomaterials or bioceramics including hydroxyapatite coating on the

metal surface possess great potential to overcome these drawbacks. Hydroxyapatite

plays a double task of inhibiting the release of metal ions, making the metallic

implant more corrosion resistant and also promoting bioactivity at the metal surface

(Sridhar et al. 1997).

The results of uncoated and coated 316L stainless steel implant with HA and

ZnFHA are presented in Tables 23.11 and 23.12. Table 23.11 compares the corro-

sion parameters from potentiodynamic polarization tests, and Table 23.12 compares

the pitting corrosion characteristics for uncoated and coated 316L stainless steel.

ZnFHA coated 316 stainless steel implant displayed lower corrosion rate, pitting

resistance than uncoated and HA coated 316L stainless steel. The corrosion resis-

tance of ZnFHA coated 316L stainless steel was found to be 115 times better than

316L stainless steel implant. The coating and passive layer both play a role in

corrosion resistance.

Figure 23.11 shows the SEM micrograph of ZnFHA coated 316L stainless steel.

Figure 23.12 displays the apatite formation on ZnFHA coating on immersion in

SBF, indicating the bioactive behavior of coating. Therefore, ZnFHA coated 316L

stainless steel can be a good candidate for bio-implant applications especially in

bone repairs in dental and orthopedics and osteoporosis treatment.

Table 23.11 Corrosion parameters from potentiodynamic polarization tests

Sample

OCP

(V)

ba

(V/decade)

bc

(V/decade)

Ecorr

(V)

jcorr

(μA/

cm²)

Corrosion rate

(mm/year)

Uncoated-

316L SS

0.324

0.335

0.8324

0.492

20.13

0.23422

HA-316L

SS

0.275

0.123

0.415

0.470

8.38

0.09732

ZnFHA-

316L SS

0.112

0.060

0.178

0.136

0.17

0.00202

Table 23.12 Pitting corrosion characterization

Sample

Breakdown potential Eb

(V)

Pit protection potential Ep

(V)

ΔE ¼ Ep – Eb

(V)

Uncoated-316L

SS

0.143

0.203

0.148

HA-316L SS

0.131

0.141

0.111

ZnFHA-316L

SS

0.251

0.158

0.093

23

Unleashing Potential of Bone Mimicking Nanodimensional Hydroxyapatites and. . .

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