ELECTROLYTIC CODEPOSITION OF ZINC AND GRAPHITE AND RESULTING PRODUCT

摘要

A high lubricity codeposit of zinc and graphite, and an improved method for depositing the codeposit. The coating is characterized by a coefficient of friction equal to or less than .130, and a high resistance to corrosion evidenced by no red rust in a salt spray environment for 72 hours and no destruction due to corrosion in an industrial environment, containing sulphur dioxide, for four months. When the codeposit additionally has a chromate outer coating, the system has a coefficient of friction equal to or less than .112 and has no red rust in a salt spray environment for at least 120 hours. The codeposit is applied by immersing a cleansed metallic substrate in an acidic zinc plating electrolyte containing at least 40 g/l zinc ions and 30-110 g/l insoluble bulk graphite, with a pH of 5-5.7. The cell of which the electrolyte is a part is energized to plate out a codeposit; the graphite is continuously agitated while in solution, the agitation being periodically interrupted to allow the graphite to settle and saturate the zinc interface as it is plating out.