Patent ID: 6716333
Filing Date: 2004-04-06
Classification: C25D

Abstract:
Method of making a wear-resistant spinning rotor cup comprising forming a hard coating on an interior surface of an incipient spinning rotor cup by (i) immersing said incipient spinning rotor in an electrolytic bath comprising a passivating agent and an electrolytic agent, wherein said passivating agent comprises a colloidal suspension of sodium silicate in the form Na2OÂ·xSiO2 (x=>2.55 by weight), and (ii) passing a modified shaped-wave alternating electric current from a source of 250 to 800 volts through said interior surface of said incipient spinning rotor, wherein said modified shaped-wave electric current rises from zero to its maximum height and falls to below 40% of its maximum height within less than a quarter of a full alternating cycle thereby causing dielectric breakdown and the formation of a ceramic coating on said interior surface, and removing said incipient spinning rotor cup from said electrolytic bath.