Abstract: An improved stainless alloy has application in handling concentrated sulfuric acid. The alloy of the invention preferably comprises 23 to 33% chromium, more than 20% nickel, 6% or more of silicon, 0.2% to 0.4% nitrogen and minor amounts of molybdenum, copper, and tungsten with the balance iron. The alloy offers superior corrosion resistance by comparison with the standard stainless steels over the range from 90% sulfuric acid into the oleum range. The alloy is readily weldable and may be used in either cast or wrought form. After heat treating the alloy acquires a duplex structure which has a mixture of austenite and ferrite phases. The heat-treated alloy is ductile.