PURPOSE: To prevent the embrittlement of a Ti material equipment and to improve the corrosion resistance without exerting unfavorable influence on the equipment, by bringing the equipment into contact with hog water contg. a specified amt. of H 2 O 2 and keeping the contact state for a prescribed time to properly form an oxide film.
CONSTITUTION: Water contg. ≤0.1wt.%, preferably about 0.5W5.0% H 2 O 2 in a tank 21 is heated to ≥50°C, preferably 50W100°C with a steam coil 25. The hot water is fed to a waste water stripper-reflux cooler 10 made of a Ti material by a pump 22. The fed hot water is passed through tubes 13 connected with a communicating chamber 11 from the inlet chamber 12A of a communicating chamber 12 having a partition wall 15. The passed hot water is returned to the tank 21 through the outlet chamber 12B of the chamber 12. This circulation of hot water is continued for a prescribed time to form an oxide film of ≥50Å, preferably 150W5,000Å thickness on the surface of the Ti material. The cooler 10 is then washed. The hot water circulating system is desirably made of stainless steel so as to inhibit oxidation.