PROBLEM TO BE SOLVED: To provide a rust preventive cleaning water, a rust preventive cleaning method and a rust preventive cleaning apparatus capable of cleaning away stains such as oils and fats deposited on metallic products, having the preventing effect on the generation of rust in cut edge faces, or the like, and capable of easily executing waste water discharging treatment, or the like. SOLUTION: When water is decomposed by using a water electrolyzer 1 having an electrolytic cell having an ion-permeable membrane between an anode and a cathode, alkali ion water of pH=8.0 to be obtained from the side of a cathode chamber is incorporated with hexavalent chromium of 10 to 200 ppm to obtain this cleaning water. By using the cleaning water, a metallic product on which working oil, or the like, is deposited is cleaned. In this case, it is preferable that the cleaning is performed, while the cleaning waste water is recovered which is returned to a storage tank 2 and is circularly used, and it is more preferable that oil floating on the surface of water in the storage tank 2 is removed by a floating oil recovering apparatus 6 and the water is circulated while oil mixed into water in the storage tank 2 is removed by an oil-water separating apparatus 9.
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