s being used for degassing of ultra-high vacuum components. The heat shield as-sembly of the furnace comprised of one molybdenum (Mo) front sheet, followed by four 304 stainless steel (SS) sheets. During prolonged service of the furnace, SS sheets developed thick black oxide scale. As a part of refurbishment drive, the SS sheets were subjected to chemical cleaning in 20 % HNO3 + 1.5 % HF, which caused severe thinning along the edges of some sheets. Detailed analysis of a damaged SS sheet showed that the damage was caused by severe sensitization of edge region which underwent extensive intergranular corrosion during chemical cleaning. Important reme-dial measures suggested to avoid similar failures included: