An Explanation of Accelerated Crevice Corrosion of Stainless Steels in Wet Limestone FGD Environments

摘要

Many steels and alloys have been used in the construction of wet limestone flue gas desulfurization (FGD) air pollution control systems ranging from duplex and austenitic stainless steels to highly alloyed grades of nickel-base corrosion-resistant alloys. The quest for cost control in power production has driven designers to the lower end of this range of materials. Some FGD absorber vessels recently constructed of duplex stainless steel have experienced severe corrosion after less than one year of operation. This attack was explored and both laboratory and field tests were conducted. Localized corrosion, especially under mineral deposits, was detected and evaluated. Samples of several grades of stainless steels and alloys were exposed in an operating scrubber vessel to determine their response to the conditions experienced in the FGD system. While the attack of the duplex steel continued, super-austenitic stainless steels and some nickel-base alloys were found to be resistant. It is also likely that contaminants in the coal may be accelerating the corrosion.