This case study focuses on the replacement of the bottom plate of a urea solution tank at Ca Mau Fertilizer Plant following a leak discovered in 2016. The investigation determined that leakage was caused by corrosion and cracking resulting from poor quality of sand beneath the tank and inadequate sealing method used to prevent ingress of rainwater between the tank bottom and the foundation. The tank, constructed with A240 304L stainless steel, exhibited localized corrosion and cracks on the outer surface of the bottom plate, where it came into contact with the sand. Notably, no corrosion was detected on the internal surface where the plate contact with the urea solution.
Failure analysis identified sulfur (S) and chloride (Cl-) impurities present in the sand as the cause of corrosion. To rectify the issue, the repair solution involved replacing the bottom plate with a new 304L stainless steel plate and completely replacing the sand layer.