Abstract: Six sets of flowing water corrosion loop have been developed which havebeer used extensively for screening tests of reactor structure material, particularlyaluminum and its alloys. This paper reports the structure of the typical loopsand the experience accumulated. The improvements of main equipments such ascirculation pumps, heaters, pressurizers valves as well as loop sealings aredescribed in detail. Also described is oxygen removing technique in loops. It isfound that the corrosion of Al is greatlly affected by flowing water.