Corrosion of stainless steel by gaseous I-2

The adsorption and desorption of gaseous iodine on stainless steel was stud ied at low temperature under atmospheric conditions. Sorption kinetics were studied by measuring the I-131 tracer activity on a stainless steel coupon during loading and purging. Scanning electron microscopy (SEM) photographs and energy dispersive X-ray (EDX) analyses were also obtained at various s tages of loading and purging. The iodine uptake and corrosion on stainless steel surface was extensive at room temperature, particularly in air. The a dsorbed iodine desorbed only during purging with air and not with N-2. This desorption behaviour and the extensive iodine-catalysed corrosion in air a re explained by the reaction of oxygen with FeI2 to form iron oxyiodide (Fe IxOy) solids, and by significant volume changes associated with the formati on of FeI2 and FeIxOy. These volume changes continuously generate cracks an d grain boundaries through which I-2 can diffuse to react with Fe. (C) 1999 Published by Elsevier Science B.V. All rights reserved.