We have been coating tubes for internal use and external sales since 1992. The galfan coating is a duplex system of a zinc aluminum alloy and then an aluminum rich primer is applied. The coating system can process 6.3499 mm (0.25 inches) to 9.52 mm (0.375 inches) diameter and 6 to 8 mm (0.2362 to 0.31496 inches) diameter tubing with 0.71119 mm (0.028 inches) to 1.0667 mm (0.042 inches) tube wall thickness.