| 摘要 |
PROBLEM TO BE SOLVED: To develop a chemical treatment solution, which can stably form a chemical conversion coating of phosphate, on a joint of a steel oil well casing containing Cr of 0.5-13%. SOLUTION: The chemical treatment solution includes a predetermined quantity of potassium ions. The method for forming the chemical conversion coating, which contains the predetermined quantity of potassium compounds and has a predetermined thickness, on the screw face of the joint of the steel oil well casing, is characterized by using the above chemical treatment solution. COPYRIGHT: (C)2003,JPO
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