1.1 ,This test method covers the evaluation of the sealing properties of enveloped gaskets for use with corrosion-resistant process equipment.2 Enveloped gaskets are described as gaskets having some corrosion-resistant covering over the internal area normally exposed to the corrosive environment. The shield material may be plastic (such as polytetrafluoroethylene) or metal (such as tantalum). A resilient conformable filler is usually used inside the envelope. The design and construction of nonmetallic gaskets is covered in Practice F336.