The removal of such anions as chloride and sulfate ions is considered to be effective for the stabilization of corrosion products in the process of conservation treatment of iron objects. Several methods of the treatment have been proposed and applied, but there is no absolute method. A method, washing with distilled water using Soxhlet system, has been developed by the authors based on the viewpoint that washing with water is simple and effective and does not damage the object during the treatment process as with the other methods. Removal of anions was examined with a Soxhlet system of test scale (10 cmphi x 19 cm height) after several experimental conditions were settled. It was found that chloride ions can be removed up to about 50% of total concentration during 20 hours of washing and that the removed percentage does not increase with more than 40 hours of washing. Since the results are clear enough and are satisfactory for the next organic functional silane treatment process, the washing system was scaled up to the size for handling armor (50 cmphi x 80 cm) and swords (22 cmphi x 120 cm). A newly developed washing system consists of a container with ion exchange resin for deionized water, a heater, a washing tank, a nitrogen gas supplier, and a vacuum pump. Its basic function is designed to be the same as with a Soxhlet system. The condition of the pure water was controlled as follows: 1) deionized water that contacts objects is heated to 80°C and is exchanged every two hours because only fresh pure water is effective in removing chloride ion from objects; 2) oxygen dissolved in pure water is expelled by heating the water, by bubbling nitrogen gas (1l/min) and by reducing air pressure (about 100 mm/Hg) within a tank to prevent corrosion during the treatment. The leaching rate of chloride and sulfate ions of the new system was found to be the same as the Soxhlet system of test scale. Such anions as chloride ions are removed by using this system. According to directions on the operation manual of the apparatus, the treatment using the new system can be completed in about 40 hours. With this method, it is possible to shorten the treatment time. And this method has no effect on the next conservation process unlike the other methods that use some kind of reagent.