Corrosion Resistance of Three High-Ni Alloys in Renewable Feedstock Pretreatment Conditions

Abstract The high alloyed grades N08935, N08825, and N06625 have been tested in an aqueous environment at T=275°C, 500 ppm of chlorides, and pH=2 adjusted using citric acid. The test environment is relevant for pre-treatment of renewable refinery feedstock for renewable diesel and sustainable aviation fuel (SAF), as well as reactor effluent air coolers (REAC’s) in hydrotreating plants. The alloys have been tested with regard to chloride induced stress corrosion cracking, (Cl-SCC), pitting, and crevice corrosion. The samples have been flat samples with ceramic crevice formers and C-rings tensioned to 100% of actual yield strength. In the paper, the results from the testing and suitability of the different grades for pretreatment and REAC applications are discussed.