FILTER DEVICE FOR CLEAN ROOM

PROBLEM TO BE SOLVED: To reduce the amount of dust generated, and improve the corrosion resistance, and reduce the cost, by forming a casing from a steel plate, whose surface is treated with hot-dip zinc coating composed of specific weight % of aluminum, silicon containing specific weight % or more of the content of aluminum, and the remainder or zinc. SOLUTION: A casing 11 is connected to a duct 30 and a blower is attached to a filter device 10. An air filter 13 is closely fixed to a fixed filter mount frame 12 in the casing 11 by means of stud bolts to put the filter 13 into the casing 11. The casing 11 of the device 10 is formed from a steel plate whose surface is treated with hot-dip zinc coating composed of 25-75 wt.% of aluminum, silicon of 0.5 wt.% or more of the content of the aluminum, and the remainder of zinc. Thus oxides of zinc prevent the corrosion of the steel plate due to its flaws or defects and a dense oxide film of aluminum prevents dust generation on the side of surface of a plated layer so that coating can be omitted, and hence cost can be reduced and the period of delivery can be shortened.