Special stainless steel grades must be used in the high pressure urea process to achieve long service life. The process conditions are highly corrosive and as the corrosion mechanism is complex, the development of suitable alloys has been concentrated in the past on refining existing grades by continuous improvement. The use of these special “urea grades" has resulted in low maintenance costs and long service life. Proper control of the process, as well as high pressure equipment manufactured with high quality products, is also needed for a long service life.
This paper discusses traditional stainless steels as well as the new alloys applied in urea processes and also elaborates on the difficult corrosive applications in urea plants.