Chromate-free type pre-coated steel sheet having excellent corrosion resistance against red rust and having a coating film excellent in moisture absorption resistance and a method for producing the same

摘要

PROBLEM TO BE SOLVED: To provide a chromate-free type precoated steel sheet exhibiting high level edge face red rust inhibition effect without generating white rust from a surface of the steel sheet, hardly generating wetness on a coated film under high moisture environment, having the coated film excellent in hygroscopic resistance and excellent in edge face red rust anticorrosion.SOLUTION: The precoated steel sheet has a plurality of coated film containing at least a chromate-free type chemical conversion treatment layer on double side of a galvanized steel sheet and a top layer coated film and an under layer coated film neighboring thereto formed on the sae, where the coated film of a single face the top coat layer satisfies conditions (1) to (4) and the under layer coated film neighboring the coated film of the top coat layer contains one or more kind of deliquescence anti rust pigment effective to suppress generation of red rust on the edge surface. (1) Contact angle to water of the coated film surface is 65 to 75°. (2) thickness of the coated film is 0.5 to 10 μm. (3) content of the pigment in the coated film is 15 to 70 mass% based on dry coated film mass. (4) total amount of ones with average primary particle diameter of 1 μm or more in the pigment is 5 mass% or more to the dry coated film mass.SELECTED DRAWING: None