Petrochemical
RAS Alloy supplies corrosion-resistant nickel alloys for chemical reactors, heat exchangers, distillation columns and acid handling systems. Grades are selected for pitting resistance, stress-corrosion cracking immunity and compliance with ASME Section VIII pressure vessel codes.
Typical Alloy Grades
C-276 / C-22 / 800H / 825 / 600
Sulfuric acid coolers and piping
Incoloy 825, Hastelloy C-276
Phosphoric acid evaporator tubes
Incoloy 825, Inconel 625
Ethylene furnace and reformer tubes
Incoloy 800H, Incoloy 800HT
Flue gas desulfurization scrubbers
Hastelloy C22, Hastelloy C-276
Chemical reactor vessels and agitators
Hastelloy B-3, Hastelloy C-276
Applicable Standards
FGD Scrubber C-276 SCC — Welding-Induced Failure
A coal-fired power plant FGD absorber vessel in Hastelloy C-276 developed chloride stress-corrosion cracking at circumferential weld seams within 24 months of operation.
Post-weld residual tensile stress exceeded 300 MPa at the weld HAZ. Combined with chloride concentration >500 ppm (from limestone slurry carryover) at 80°C, the residual stress exceeded the chloride SCC threshold for C-276 in the as-welded condition.
RAS Alloy now recommends full solution anneal at 1120°C with rapid water quench after welding for C-276 vessels operating above 60°C with >200 ppm chlorides. For new FGD projects, Hastelloy C22 is specified for its superior oxidizing media resistance and as-welded SCC immunity.