The appearance of zinc ash refers to the formation of strip or point inclusions along the longitudinal direction on the surface of galvanized steel plate, which is a slight defect, but its occurrence frequency is higher than other slag defects. The reason is that the slag on the head zinc level and the solid zinc slag condensed in the head cavity act together to produce the zinc ash. The zinc slag falls on the surface of the strip steel, causes slight indentation with the strip steel through the sink roll of the zinc pot, or generates strip or spot inclusions along the longitudinal direction of the surface of the zinc plate, causing the zinc ash defect The control measures are as follows: 1. The optimized humidification system of nitrogen humidification system at the furnace head can increase the dew point temperature, make zinc vapor form a protective film on the surface of zinc liquid, and restrain the continuous evaporation of zinc liquid. When the dew point temperature is not controlled properly, excessive water vapor may cause defects. Therefore, the proper dew point temperature of furnace head should be determined in actual production 2. Cleaning of zinc slag at furnace head 1) make a special desilting spoon and clean the slag at furnace head 2-3 times per shift. 2) add the zinc slag adsorption and removal device at the furnace head, and blow the external hot air into the closed furnace head through the fan 3) use the shutdown time to reduce the zinc pot, expose the zinc position at the furnace head, and then manually remove the slag Galvanized coil 3. Temperature control of steel strip into the pot 1) strictly control the temperature of steel strip into the zinc pot, because the temperature of steel strip exceeds the temperature of zinc liquid by more than 20 degrees, not only the temperature of zinc pot will increase, but also the zinc content will increase. 2) strictly control the temperature of zinc pot, not exceeding (465 + 2) Celsius, reduce the temperature fluctuation of zinc liquid and prevent the formation of zinc slag 4. The composition control of zinc solution has a great relationship with zinc ash. The control range of common galvanized sheet is 0.19-0.22%, and that of alloy galvanized sheet is 0.10-0.15%. 5. The decrease of zinc level in the frequency control of zinc pot will make the internal slag of the nose adhere to the inner wall of the nose. Therefore, the zinc adding frequency should be determined reasonably according to the zinc liquid consumption rate to prevent the fluctuation of water level in the upstream and downstream of the zinc liquid and the accumulation of slag in the inner wall of the head.