Intermediate light oil such as naphtha and gas oil from either atmospheric distillation unit fluid catalytic cracking unit or delayed coking unit is usually temporally stored in storage tanks for further processing. Content of corrosiveness of intermediate light oil increases as a result of low-grade crudes with increased amount and decreased crude quality being processed. Experiments were carried on under simulated environment to understand corrosion characteristics of intermediate light oil in storage tank. Factors such as sulfur content (both mercaptan and sulfide ion) chloride water temperature were investigated. The operational up-limit of sulfur for storage tank was set at 0.5wt% based on the experiment results.