an adherent bioactive calcium phosphate coating is formed on a titanium or titanium alloy substrate by immersing the substrate in an acidic calcium phosphate solution to form a non - apatitic calcium phosphate coating on the substrate . in a second step the coated substrate can be converted to a less reactive coating by being immersed into a basic or neutral solution to convert the coating into an apatite . however if a relatively reactive coating is desired , the second step can be dispensed with .