Methods and systems comprising a first and a second powder coating apparatus, with each apparatus comprising a tubular barrel having an axial bore extending longitudinally therethrough, are usable for coating an interior surface of a tubular member. Each coating apparatus comprises a conical member connected with the tubular barrel and at least one gas conduit connected to the tubular barrel for communicating gas into the tubular barrel. The at least one gas conduit contains a gas flow control valve connected thereto for controlling the volumetric flow rate of gas through the at least one gas conduit. Each coating apparatus further comprises at least one container for holding a coating material, an inlet conduit for communicating the coating material into the axial bore of the tubular barrel, and a plurality of gas nozzles connected to the tubular barrel for inducing spiraling gas flow through the axial bore of the tubular barrel.

Apparatus and methods are disclosed which apply inorganic particles to a plugged honeycomb body comprising porous walls, an inlet end and an outlet end. The apparatus comprises a Venturi tube through which the particles flow into a duct system. Filtration articles comprise: a plugged honeycomb body; inorganic deposits disposed within the plugged honeycomb filter body having a porosity in a range of greater than 95% to less than or equal to 99.9% and an average thickness in a range of greater than or equal to 0.5 m to less than or equal to 50 m; and a clean filtration efficiency of greater than or equal to 85% as measured by a smoke filtration efficiency test.