Method and system for coating internal surfaces of prefabricated process piping in the field

摘要

The coating of internal surfaces of a workpiece is achieved by connecting a bias voltage (20) such that the workpiece functions as a cathode and by connecting an anode (22 and 24) at each opening of the workpiece. A source gas (16 and 18) is introduced at an entrance opening, while a vacuum source (32) is connected at an exit opening. Pressure within the workpiece is monitored (34) and the resulting pressure information is used for maintaining a condition that exhibits the hollow cathode effect. Optionally, a pre-cleaning may be provided by introducing a hydrocarbon mixture and applying a negative bias to the workpiece, so as to sputter contaminants from the workpiece using argon gas (16). Argon gas may also be introduced during the coating processing to re-sputter the coating, thereby improving uniformity along the length of the workpiece. The coating may be a diamond-like carbon material having properties which are determined by controlling ion bombardment energy.