Abstract: The invention is a method, involving temperatures between room temperature and 100.degree. C., for coating a metal substrate with hydroxyapatite. The intended application is coating porous metal coats of orthopedic and endosseous implants such that the underlying metal is not sintered and the hydroxyapatite coating has chemical and physical properties that are close to biological apatite. The method involves: (i) cleaning the metal substrate, (ii) coating the metal substrate with brushite by electrodeposition at room temperature, (iii) dislodging bubbles periodically during brushite electrodeposition, and (iv) converting the brushite coating to hydroxyapatite at a temperature between room temperature and 100.degree. C.

Abstract: An electrochemical cell having improved current efficiency and a method for electrochemically reacting a liquid electrolyte with a gas in an electrochemical cell. The cell has at least two electrodes separated by a cell separator wherein at least one of said electrodes is a porous, self-draining, gas diffusion electrode. In one embodiment of the invention, an electrolyte is flowed through said cell separator into a porous, self-draining electrode and simultaneously the electrode is fed with a mixture of a reactive gas and water or an electrolyte. In another embodiment of the invention in which the cell separator is an ion exchange permselective membrane, a mixture of a reactive gas and an electrolyte are fed to the porous, self-draining electrode. Preferably said porous, self-draining electrode is a cathode.