| CPC C23D 5/04 (2013.01) [C23C 4/02 (2013.01); C23C 4/04 (2013.01); C23C 4/129 (2016.01); C23C 4/16 (2013.01); C23C 4/18 (2013.01); C23D 3/00 (2013.01); C23D 5/005 (2013.01); C23D 15/00 (2013.01); H05B 6/10 (2013.01); H05B 6/104 (2013.01); H05B 6/14 (2013.01); H05B 6/36 (2013.01); H05B 6/42 (2013.01); H05B 6/44 (2013.01); B05D 1/12 (2013.01); B05D 3/0245 (2013.01); B05D 7/222 (2013.01); B05D 2202/10 (2013.01); F16L 58/14 (2013.01)] | 4 Claims |

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1. A method of applying a vitreous coating to a metal pipe by a dry process using induction heating and electrostatic sprayers, the method comprising:
advancing an induction heating apparatus along an interior surface of a metal pipe, wherein the induction heating apparatus comprises at least one ring-shaped induction coil, a first baffle and second baffle, wherein the first baffle and second baffle at least partially and circumferentially seal off a portion of the interior surface of the metal pipe in proximity to the at least one ring-shaped induction coil, wherein an enclosed processing area is proximate to the at least one ring-shaped induction coil, wherein the enclosed processing area includes at least one electrostatic sprayer;
energizing the at least one ring-shaped induction coil to controllably heat the interior surface of the metal pipe in proximity to the enclosed processing area;
energizing the least one electrostatic sprayer and electrostatically spraying a dry frit onto the interior surface of the metal pipe; and
forming a vitreous coating on the interior surface of the metal pipe from the dry frit by fusing the dry frit onto the interior surface of the metal pipe as the induction heating apparatus advances along the interior surface of the metal pipe.
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