SURFACE TREATED STEEL PRODUCT, METHOD FOR PRODUCTION THEREOF AND CHEMICAL CONVERSION TREATMENT SOLUTION

摘要

A chemical conversion film having a specified thickness and containing a potassium compound in a specified amount is formed on the surface of a screw of a joint portion of an oil well steel pipe by using a chemical conversion treatment solution added with a potassium ion in a specified amount. The chemical conversion treatment solution allows the stable formation of a phosphate chemical conversion film on a joint portion of an oil well pipe steel product which contains 0.5 to 13 % of Cr.