Here I have found some pretty well described technique, but it is pretty wide to copy it here. So, please, use the following link:
Article Biomimetic Apatite Coating on Metal Implants
Here are some other important links:
Article A comprehensive review of hydroxyapatite-based coatings adhe...
If you have found current answer as useful, please, do not hesitate to recommend it. That will help other researches to find the best answer, according to their purposes. Best of luck in your research!
The most popular method for coating of hydroxyapatite powder on a metal substrate is plasma spraying method which exhibits some important drawbacks: the inability to cover porous implants and to incorporate biologically active agents and particle release.
Plasma spray coating and electrostatic spray coating methods can be used for coating on Mg alloys such as AZ31 and AZ91. Here are 2 manuscript of a friend (@Serkan Baslayici) :