How to choose.
If a finishing shop stocks only one masking tape, it is almost always green polyester. PET film backing carries silicone adhesive that survives the powder-coating cure cycle and then peels away in one piece, leaving a sharp coating edge and a clean surface. It is the reference point every other masking tape gets compared against.
What PET tape does best
Flat faces, gasket surfaces, machined pads and gently curved edges are ideal PET territory. The film backing resists the coating chemistry and oven heat, and because the backing does not stretch much, the paint line stays where you laid it. Die-cut PET discs and dots extend the same behaviour to round features — much faster to apply than cutting tape by hand.
Its limits — and what to use instead
Above roughly 204°C sustained, PET softens; step up to polyimide film for PCB work or unusually hot processes. On complex 3D contours the stiff film backing fights you; a washi or crepe paper tape conforms better. And inside holes and threads, no tape competes with a molded plug — taping threads is the single most common masking mistake we see in incoming RFQs.
Ordering notes
Specify width, length per roll and quantity; common widths ship from stock and custom slitting is quick work. If you are masking to a dimension repeatedly, ask about die-cut shapes instead of rolls — the per-part cost is often lower once application labour is counted.
