| 摘要 |
PROBLEM TO BE SOLVED: To reduce water discharging cost, to protect the environment and furthermore to lessen an installing space for a waste water treatment plant required heretofore by reducing the use quantity of washing water and a rust preventive in washing electronic parts and/or mechanical parts and reducing the generated quantity of waste water in rinsing. SOLUTION: A rust preventive in which its solubility in water is >=0.1g rust preventive/100g water at 0 deg.C and pH of water solution of the rust preventive of 0.1g rust preventive/100g water is within the range of 3∼13 and washing liquid containing a surfactant are used to wash oily soiling stuck on a material to be washed. When regenerating the washing liquid containing insoluble oily soiling generated by this washing, the washing liquid is subjected to centrifugal separation, allowing the oily fouling to be classified and removed from the washing liquid.
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