Previously corrosion resistant liquid coatings have been applied to steel fasteners such as bolts by placing a quantity of bolts in a cage with a perforate bottom and a cylindrical sidewall, dipping the cage and bolts in a pool of liquid coating, and then rotating the cage with the bolts therein at a relatively high speed of about 200 to 500 RPM to remove excess liquid coating from the bolts by centrifugal force. Thereafter the coated bolts were removed from the cage and heated in a furnace to a peak metal temperature of 325.degree. to 450.degree. F. for about 20 minutes to cure the liquid coating to a dry film adhered to the bolts. Previously the liquid coating has also been applied by rotating a cage with a quantity of bolts therein while pouring a stream of liquid coating on the bolts. After sufficient coating has been poured to cover all of the bolts, rotation of the cage is continued to remove excess coating from the bolts by centrifugal force.
These previously known methods cannot satisfactorily apply a liquid coating to fasteners having a blind hole or recess therein such as a socket in the head of a fastener for driving it. Typically these internal drive sockets are known as Torx, Phillips, Cross, Hex, Allen, Robertson, and the like head screws, cap screws, bolts, and other fasteners. With these prior methods excess liquid coating accumulates in the blind holes or sockets and when cured results in a dry film which is too thick. The thick dry film often makes it more difficult to insert a driving tool in the socket and more importantly is frequently scraped off the fastener or scratched sufficiently so that its ability to provide corrosion resistance is greatly impaired and frequently destroyed. If the coating is intended to provide a desired color or finish for decorative purposes, this scraping or scratching is also unacceptable.
Because the results of these previous methods were unacceptable, fasteners with blind holes or sockets had to be electroplated at considerable cost with metal coatings such as nickel and chrome to provide satisfactory corrosion resistance and/or decorative appearance.