Method and apparatus for differentially and simultaneously electrocoating the interior and exterior of a metal container

DETAILED DESCRIPTION In accordance with the present invention, a method and apparatus are provided for simultaneously electrocoating the interior and exterior of a metal container.
The method and apparatus also provide for a coating weight differential between the interior and exterior surfaces of a container.
A container is positioned with its open end down, an electrically conductive probe, including a nozzle, is inserted therein, and an outer electrically conductive housing encloses the container such that continuous passageways are formed leading from the nozzle of the probe to the interior of the container to the exterior of the container.
Electrocoating material may be flowed through the nozzle into the container interior to fill the continuous passageways from the interior of the container to the exterior of the container creating a transient bath which floods the entire container in electrocoating material.
The probe-nozzle and the outer housing are electrically charged of the same polarity.
An electrical potential is simultaneously impressed between the container and the probe and between the container and the outer housing resulting in the interior and exterior of the container being electrocoated.
Imposition of different electrical potentials results in differential coating of the interior and exterior of the container.
An object of the invention is to provide a method and apparatus for electrocoating the interior and exterior of the metal container simultaneously in one rapid operation which is suitable for high speed production.
Another object of the invention is to facilitate electrocoating of a metal container with a uniform coating having a controlled coating weight.
A further object of the invention is to simultaneously and differentially electrocoat the interior and exterior of a metal container.