Anti-corrosion treatment liquid for welded steel pipe, chemical treatment method of welded steel pipe, molded product of welded steel pipe and welded steel pipe

摘要

An object of the present invention is to provide a rust-preventing treatment liquid for welded steel pipes that can further improve the weather resistance of a chemical conversion treatment film. The above object is an organic resin containing a fluororesin, a compound containing a group 4 element or an ion of a group 4 element, an ester compound of adipic acid or phthalic acid and an alcohol having 1 to 3 carbon atoms, and n- It contains at least one binding accelerator selected from the group consisting of methyl-2-pyrrolidone, and the content of the compound containing the Group 4 element or the ions of the Group 4 element is 0.5 g/L or more in terms of metal atoms. 6 g/L or less, and the sum of the content of the compound containing the group 4 element in terms of metal atoms of the ions of the group 4 element and the content of the bonding accelerator is 20 g/L or less Is achieved.