High adhesion amount plating method and plating bath of molten Al-Zn-Si alloy and the molten Al-Si alloy by the flux method

摘要

PURPOSE: To form hot dip alloy coating film layers having a high coating weight and excellent smoothness by removing the oxidized films of iron and steel materials, adjusting their surfaces to specific surface roughness, subjecting the surfaces to an activation treatment and subjecting the iron and steel materials to an immersion treatment into a hot dip coating bath contg. a specific quantity of iron component, thereby controlling the coating weight of plating. ;CONSTITUTION: The average roughness of the surfaces of the iron and steel materials from which the oxidized film are removed is adjusted to 2.5 to 7.5μmRa and thereafter, the surfaces are activated. An iron-component of 0.25 to 1.5 outer weight % of the total weight of the plating bath exclusive of a flux is melted and added into the hot dip coating bath. The iron and steel materials are subjected to the immersion treatment into the hot dip coating bath. The hot dip coating bath is a molten Al-Zn-Si alloy molten Al-Si alloy for which the flux is used. The treatment to control the coating weight of the plating is then executed. The treatment for the control is executed for the specified time by a centrifugal sepn. method of a circumferential speed of 400 to 1500m/minute. The circumferential speed is thereafter changed to 1/3 to 4/5 and the treating time to 1/5 to 3/4 and the treatment is executed by the centrifugal sepn. method of backward rotation.;COPYRIGHT: (C)1996,JPO