JPS6418475A - Coating method for rust preventive - Google Patents

Abstract

PURPOSE:To form a uniform rust-preventive coating cover the inside of a hollow structure having openings, by spraying a pressurized mixture of a rust preventive and a blowing agent on the inner surfaces of the hollow structure by means of a nozzle which has been inserted into the hollow structure through one of the openings and which has a spray pattern capable of covering all the inner surfaces of the hollow structure. CONSTITUTION:A spray nozzle 6 is inserted into a hollow structure 20 through one of openings 21 provided in a side wall of the hollow structure 20 at a pitch of 300-600mm, and then a mixture of a rust preventive A and a blowing agent B is sprayed on the inner surfaces of the walls of the hollow structure 20 at a discharge pressure of 10-40kg/cm<2>, thereby to perform coating and blowing. In these procedures, first spraying is carried out with the nozzle 6 placed at a first position, and then second spraying is performed after the nozzle is further advanced to a deeper position (6'). Thus, the mixture is sprayed on all the inner surfaces of the walls of the structure 20. Accordingly, a uniform rust- preventive coating can be formed over the whole inner surfaces of the walls by spraying once or twice for each opening at a discharge pressure of 10kg/cm<2>, for 0.3-0.5sec each.