Composition and process for mechanical plating of cobalt-containing coatings on metal substrates

A process for mechanically plating metal articles comprising:

• introducing said metal articles to be mechanically plated, a quantity of impact media, a co-plating promoter composition, powdered zinc and sufficient water to form a slurry into a rotatable drum, said co-plating promoter composition comprising from 0.1 to 10 wt-% insoluble cobalt compound, from 10 to 60 wt-% platable tin compound, from 10 to 45 wt-% acidity regulating agent, and from 10 to 60 wt-% dispersant;
• rotating said drum to tumble said articles in said slurry for a period of time sufficient to apply a zinc-, tin- and cobalt-containing coating to said articles;
• and
• recovering mechanically plated articles from said slurry.