Shop coated steel plate having good corrosion resistance and weather-proof

A method of producing a shop coated steel plate is given and comprises pretreatment, shop-coating and electron beam irradiation in order to provide material for shipbuilding and other construction. A steel plate treated by surface cleaning is first applied with a nickel, chromic or chemical inner layer and then secondarily applied with an electron beam-polymerizable outer layer. In one embodiment, a 9 mm thick hot rolled plate for shipbuilding was shot-blasted with a 1-1.2 mm phi steel grid so as to have a surface roughness of about 50μ and at least a 95% degree of surface cleanliness. The plate was nickel plated to a 0.08μ thickness at 900C for 10 sec. An acryl-epoxy-butyral coating material was sprayed onto the nickel plated steel to a thickness of 20μ and then irradiated with electron beams at energy levels of 2, 5 and 10 Mrad. As a result of a salt solution spraying test, no change was not found after one week. Exposure tests revealed weather proofness double or triple of that of an unpretreated sample. (Iwakiri, K.)