Patent ID: 6893551

Claim:
An improved process for forming ceramic composite coatings on bodies of reactive metals and alloys which comprises: electrolysing in a non-metallic, non-reactive, non-conductive reaction chamber containing an alkaline electrolytic solution having a pH>12 and conductivity>2 millimhos, comprising potassium hydroxide, sodium tetra silicate and de-ionized or distilled water; immersing at least two metallic bodies selected from the reactive group of metals on which coatings have to be effected, the bodies being fixed in a movable manner, each body being connected to an electrode; passing wave multiphase alternating current across the said bodies by means of two back-back parallelly connected thyristors for a period based on the desired thickness of the coatings to be achieved, slowly increasing the current being supplied to the said bodies till the required current density is achieved, then maintaining the current at the same level throughout the process, the electric potential being further increased gradually to compensate the increasing resistance of the coating when the visible arcing at the surface of the immersed regions of the said bodies is noticed; regulating the composition of the electrolyte by measuring its pH and conductivity during the process by conventional methods, maintaining the temperature of the electrolyte between the range of 4 degree C. to 50 degree C. and keeping the electrolyte in continuous circulation throughout the process.