Discoloration and its prevention by surface treatment in high-purity water systems

The interior surfaces of distillation units in pharmaceutical water systems are continuously exposed to hot, highly purified water and steam. This article describes an investigation of how various surface pretreatment inhibit the rate of discoloration of the process contact surfaces of SUS316L stainless steel water distillation equipment. Historically, well-polished metal surfaces have been used in high-purity water systems. The results of this study suggest, however, that portions of these systems, particularly surfaces in contact with hot, high-purity water or steam, will exhibit less discoloration and surface build-up if those surfaces are pretreated with pickling and passivation but not buffing.