Masking is a critical preparatory technique used in the galvanizing of tubes and pipes to intentionally prevent the molten zinc from adhering to specific areas of the steel component.
Purpose and Method
Masking is necessary when parts of the pipe must remain uncoated to ensure proper functionality or assembly:
Thread Protection: The most common application is protecting internal threads on a pipe end (in hot dip galvanizing process). If the threads were galvanized, the added thickness of the zinc coating would interfere with or prevent a nut or fitting from being screwed on, requiring costly and time-consuming re-tapping.
Mating Surfaces: It is also used on precision mating surfaces or areas requiring subsequent welding.
The method involves covering the critical area with a temporary barrier material, such as high-temperature resistant tape, paint, plugs, or caps, before the pipe is immersed in the molten zinc. After galvanizing and cooling, the masking material is removed, leaving the underlying surface bare and perfectly sized for its intended purpose.