| 摘要 |
PROBLEM TO BE SOLVED: To suppress harmful gaseous NOx from a pickling liquid and to improve a pickling environment by maintaining the Fe<3+> /Fe<2+> ratio and nitric acid concn. in the pickling liquid prepd. using the nitric acid at a specific relation. SOLUTION: The relation between the Fe<+3> /Fe<+2> ratio and HNO3 concn. in the pickling liquid prepd. by using the nitric acid is so regulated as to maintain [Fe<+3> /Fe<+2> ]>=1.4×[NHO3 concn.(wt./vol.%]-1.7. Further, oxidizing agents not contg. nitrogen or nitric acid ions, for example, hydrogen peroxide water, dichromic acid, permanganic acid are added to the pickling liquid or hydrogen fluoride is added to the pickling liquid. As a result, the generation of the gaseous NOx from the pickling liquid is suppressed and the pickling to the treating materials may be effectively executed. Further, the generation of the NOx may be suppressed as well even at the time of pickling of steel products contg. less Ni liable to generate the gaseous NOx as a pickling material.
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