There are certain types of evaporators which are too demanding for aus­tenitic stainless steel. For these processes titanium and, more recently, zir­conium are used (Baldev, 2006). These materials have an extremely high resistance to nitric acid corrosion (zirconium is virtually immune to corro­sion in pure nitric acid). However, serious problems can arise in the pres­ence of impurities such as fluorides, and great care is needed to ensure correct process chemistry. These materials are very expensive and can be difficult to fabricate without the necessary know-how, i. e. only companies with the relevant expertise are capable of manufacturing high integrity plant and equipment in these materials. Zirconium, in the form of specially designed rings formed from strip, is used in packed columns to supply a large surface area on which condensation can occur. The older packing material, stainless steel, contributed significant quantities of iron to the process fluids even though their corrosion rate was very low and this iron, added to the process liquor, could enhance the corrosion of stainless steel vessels and pipework. Zirconium has virtually zero corrosion even in nitric acid vapor.