High-chromium alloy developed against intergranular attack in nuclear steam generators and nitric/HF service.
690 carries about 30 % chromium, which is what makes it resistant to intergranular corrosion and intergranular stress-corrosion cracking in high-temperature water — the failure mode that limited 600 in pressurised-water reactor steam generators. It has been the standard steam-generator tubing material for PWR plants since the 1990s.
Outside nuclear work, it is used in nitric acid and nitric/HF pickling service, where the high chromium content gives it an advantage over 600.
ASTM B564, B166, B167, B168; ASME Section III for nuclear components
The default alloy for mixed acids, chlorides and wet chlorine — and the grade most often specified when no one is sure what the stream will do.
Alloy detailChromium-rich cousins of C-276: better in oxidising media and in wet chlorine, with C-4 for hot ductility.
Alloy detailNickel–molybdenum alloys for hydrochloric acid — any concentration, any temperature within the practical range.
Alloy detailQuotes within one business day. Send grade, size, pressure class, face type and quantity — a drawing works better than a description.
