Isothermal capsules have been used by many investigators for studying high-temperature aqueous corrosion of steam generator tube materials in nuclear power stations. Pitting of Inconel(1) 600 (UNS(2) N06600) and 690 (UNS N06690) tubing has been studied in isothermal capsules.1 Steam generator tube denting caused by the accelerated corrosion of carbon steel support structures has also been studied extensively in isothermal capsules.2-5
Although details of capsule design vary among different laboratories, the general features of a capsule, as shown in Figure 1 are similar. The capsule normally consists of a short length of tubing material (up to 40 cm) with solid plugs or caps connnected to both ends. Prior to attaching both end caps, the tube is filled with an aqueous solution of predetermined composition. The capsule is then placed in an oven or other heating device for maintaining the test temperature (up to 350°C). Coupons or...
